chore: cherry-pick 6bb320d134b1 from chromium (#32009)

* chore: cherry-pick 6bb320d134b1 from chromium

* chore: update patches

Co-authored-by: PatchUp <73610968+patchup[bot]@users.noreply.github.com>
Co-authored-by: Electron Bot <electron@github.com>

patches/chromium/.patches

@@ -121,6 +121,7 @@ cherry-pick-1a8af2da50e4.patch
 cherry-pick-a5f54612590d.patch
 cachestorage_store_partial_opaque_responses.patch
 fix_aspect_ratio_with_max_size.patch
+cherry-pick-6bb320d134b1.patch
 cherry-pick-109fde1088be.patch
 m96_fileapi_move_origin_checks_in_bloburlstore_sooner.patch
 cherry-pick-f781748dcb3c.patch

patches/chromium/cherry-pick-6bb320d134b1.patch

@@ -0,0 +1,765 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Victor Costan <pwnall@chromium.org>
+Date: Thu, 11 Nov 2021 00:22:30 +0000
+Subject: M96: Storage Foundation: Share FileState ownership with I/O threads.
+
+blink::NativeIOFile methods implementing the Storage Foundation
+JavaScript API pass raw pointers to NativeIOFile::FileState instances to
+their corresponding blink::NativeIOFile::Do*() methods, which rely on
+that CrossThreadPersistent<NativeIOFile> arguments to keep the
+underlying NativeIOFile::FileState instances alive.
+
+CrossThreadPersistent can be used across threads to keep a garbage
+collected object alive, together with any non-garbage-collected objects
+that it owns. However, relying on CrossThreadPersistent existence to
+access the owned objects on a different thread is not safe.
+cppgc::subtle::CrossThreadPersistent (blink::CrossThreadPersistent is an
+alias to that) has comments explaining that the garbage collected heap
+can go away while the CrossThreadPersistent instance exists.
+
+This CL fixes the problem by having the ownership of
+NativeIOFile::FileState be shared between the corresponding NativeIOFile
+instance and any threads doing I/O on the FileState.
+
+(cherry picked from commit 7dc02206707362f3f92cea93f8eb2fa4af0d375f)
+
+Bug: 1240593
+Change-Id: I5c9c818bcb23316fe1fd5afa57ed9c3fdb034377
+Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3269947
+Commit-Queue: Victor Costan <pwnall@chromium.org>
+Reviewed-by: Austin Sullivan <asully@chromium.org>
+Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
+Reviewed-by: enne <enne@chromium.org>
+Cr-Original-Commit-Position: refs/heads/main@{#940130}
+Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3272672
+Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
+Cr-Commit-Position: refs/branch-heads/4664@{#945}
+Cr-Branched-From: 24dc4ee75e01a29d390d43c9c264372a169273a7-refs/heads/main@{#929512}
+
+diff --git a/third_party/blink/renderer/modules/native_io/native_io_file.cc b/third_party/blink/renderer/modules/native_io/native_io_file.cc
+index 4d5aa4efa13930aea4886bac0fd8ba892ce8b5a5..615c1d3a20cba732a3d981bf6b2df181e56d2727 100644
+--- a/third_party/blink/renderer/modules/native_io/native_io_file.cc
++++ b/third_party/blink/renderer/modules/native_io/native_io_file.cc
+@@ -9,6 +9,7 @@
+ #include "base/check.h"
+ #include "base/files/file.h"
+ #include "base/location.h"
++#include "base/memory/scoped_refptr.h"
+ #include "base/numerics/checked_math.h"
+ #include "base/sequenced_task_runner.h"
+ #include "base/task/thread_pool.h"
+@@ -47,31 +48,167 @@
+ 
+ namespace blink {
+ 
+-struct NativeIOFile::FileState {
+-  explicit FileState(base::File file) : file(std::move(file)) {}
++// State and logic for performing file I/O off the JavaScript thread.
++//
++// Instances are allocated on the PartitionAlloc heap. Instances cannot be
++// garbage-collected, because garbage collected heaps get deallocated when the
++// underlying threads are terminated, and we need a guarantee that each
++// instance remains alive while it is used by a thread performing file I/O.
++//
++// Instances are initially constructed on a Blink thread that executes
++// JavaScript, which can be Blink's main thread, or a worker thread. Afterwards,
++// instances are (mostly*) only accessed on dedicated threads that do blocking
++// file I/O.
++//
++// Mostly*: On macOS < 10.15, SetLength() synchronously accesses FileState on
++// the JavaScript thread. This could be fixed with extra thread hopping. We're
++// not currently planning to invest in the fix.
++class NativeIOFile::FileState
++    : public base::RefCountedThreadSafe<NativeIOFile::FileState> {
++ public:
++  explicit FileState(base::File file) : file_(std::move(file)) {
++    DCHECK(file_.IsValid());
++  }
+ 
+   FileState(const FileState&) = delete;
+   FileState& operator=(const FileState&) = delete;
+ 
+   ~FileState() = default;
+ 
++  // Returns true until Close() is called. Returns false afterwards.
++  //
++  // On macOS < 10.15, returns false between a TakeFile() call and the
++  // corresponding SetFile() call.
++  bool IsValid() {
++    DCHECK(!IsMainThread());
++
++    WTF::MutexLocker locker(mutex_);
++    return file_.IsValid();
++  }
++
++  void Close() {
++    DCHECK(!IsMainThread());
++
++    WTF::MutexLocker locker(mutex_);
++    DCHECK(file_.IsValid()) << __func__ << " called on invalid file";
++
++    file_.Close();
++  }
++
++  // Returns {length, base::File::FILE_OK} in case of success.
++  // Returns {invalid number, error} in case of failure.
++  std::pair<int64_t, base::File::Error> GetLength() {
++    DCHECK(!IsMainThread());
++
++    WTF::MutexLocker mutex_locker(mutex_);
++    DCHECK(file_.IsValid()) << __func__ << " called on invalid file";
++
++    int64_t length = file_.GetLength();
++    base::File::Error error =
++        (length < 0) ? file_.GetLastFileError() : base::File::FILE_OK;
++
++    return {length, error};
++  }
++
++  // Returns {expected_length, base::File::FILE_OK} in case of success.
++  // Returns {actual file length, error} in case of failure.
++  std::pair<int64_t, base::File::Error> SetLength(int64_t expected_length) {
++    DCHECK(!IsMainThread());
++    DCHECK_GE(expected_length, 0);
++
++    WTF::MutexLocker mutex_locker(mutex_);
++    DCHECK(file_.IsValid()) << __func__ << " called on invalid file";
++
++    bool success = file_.SetLength(expected_length);
++    base::File::Error error =
++        success ? base::File::FILE_OK : file_.GetLastFileError();
++    int64_t actual_length = success ? expected_length : file_.GetLength();
++
++    return {actual_length, error};
++  }
++
++#if defined(OS_MAC)
++  // Used to implement browser-side SetLength() on macOS < 10.15.
++  base::File TakeFile() {
++    WTF::MutexLocker mutex_locker(mutex_);
++    DCHECK(file_.IsValid()) << __func__ << " called on invalid file";
++
++    return std::move(file_);
++  }
++
++  // Used to implement browser-side SetLength() on macOS < 10.15.
++  void SetFile(base::File file) {
++    WTF::MutexLocker locker(mutex_);
++    DCHECK(!file_.IsValid()) << __func__ << " called on valid file";
++
++    file_ = std::move(file);
++  }
++#endif  // defined(OS_MAC)
++
++  // Returns {read byte count, base::File::FILE_OK} in case of success.
++  // Returns {invalid number, error} in case of failure.
++  std::pair<int, base::File::Error> Read(NativeIODataBuffer* buffer,
++                                         int64_t file_offset,
++                                         int read_size) {
++    DCHECK(!IsMainThread());
++    DCHECK(buffer);
++    DCHECK_GE(file_offset, 0);
++    DCHECK_GE(read_size, 0);
++
++    WTF::MutexLocker mutex_locker(mutex_);
++    DCHECK(file_.IsValid()) << __func__ << " called on invalid file";
++
++    int read_bytes = file_.Read(file_offset, buffer->Data(), read_size);
++    base::File::Error error =
++        (read_bytes < 0) ? file_.GetLastFileError() : base::File::FILE_OK;
++
++    return {read_bytes, error};
++  }
++
++  // Returns {0, write_size, base::File::FILE_OK} in case of success.
++  // Returns {actual file length, written bytes, base::File::OK} in case of a
++  // short write.
++  // Returns {actual file length, invalid number, error} in case of failure.
++  std::tuple<int64_t, int, base::File::Error> Write(NativeIODataBuffer* buffer,
++                                                    int64_t file_offset,
++                                                    int write_size) {
++    DCHECK(!IsMainThread());
++    DCHECK(buffer);
++    DCHECK_GE(file_offset, 0);
++    DCHECK_GE(write_size, 0);
++
++    WTF::MutexLocker mutex_locker(mutex_);
++    DCHECK(file_.IsValid()) << __func__ << " called on invalid file";
++
++    int written_bytes = file_.Write(file_offset, buffer->Data(), write_size);
++    base::File::Error error =
++        (written_bytes < 0) ? file_.GetLastFileError() : base::File::FILE_OK;
++    int64_t actual_file_length_on_failure = 0;
++    if (written_bytes < write_size || error != base::File::FILE_OK) {
++      actual_file_length_on_failure = file_.GetLength();
++      if (actual_file_length_on_failure < 0 && error != base::File::FILE_OK)
++        error = file_.GetLastFileError();
++    }
++
++    return {actual_file_length_on_failure, written_bytes, error};
++  }
++
++  base::File::Error Flush() {
++    DCHECK(!IsMainThread());
++
++    WTF::MutexLocker mutex_locker(mutex_);
++    DCHECK(file_.IsValid()) << __func__ << " called on invalid file";
++
++    bool success = file_.Flush();
++    return success ? base::File::FILE_OK : file_.GetLastFileError();
++  }
++
++ private:
+   // Lock coordinating cross-thread access to the state.
+-  WTF::Mutex mutex;
++  WTF::Mutex mutex_;
++
+   // The file on disk backing this NativeIOFile.
+-  //
+-  // The mutex is there to protect us against using the file after it was
+-  // closed, and against OS-specific behavior around concurrent file access. It
+-  // should never cause the main (JS) thread to block. This is because the mutex
+-  // is only taken on the main thread in CloseBackingFile(), which is called
+-  // when the NativeIOFile is destroyed (which implies there's no pending I/O
+-  // operation, because all I/O operations hold onto a Persistent<NativeIOFile>)
+-  // and when the mojo pipe is closed, which currently only happens when the JS
+-  // context is being torn down.
+-  //
+-  // TODO(rstz): Is it possible and worthwhile to remove the mutex and rely
+-  // exclusively on |NativeIOFile::io_pending_|, or remove
+-  // |NativeIOFile::io_pending_| in favor of the mutex (might be harder)?
+-  base::File file GUARDED_BY(mutex);
++  base::File file_ GUARDED_BY(mutex_);
+ };
+ 
+ NativeIOFile::NativeIOFile(
+@@ -81,7 +218,7 @@ NativeIOFile::NativeIOFile(
+     NativeIOCapacityTracker* capacity_tracker,
+     ExecutionContext* execution_context)
+     : file_length_(backing_file_length),
+-      file_state_(std::make_unique<FileState>(std::move(backing_file))),
++      file_state_(base::MakeRefCounted<FileState>(std::move(backing_file))),
+       // TODO(pwnall): Get a dedicated queue when the specification matures.
+       resolver_task_runner_(
+           execution_context->GetTaskRunner(TaskType::kMiscPlatformAPI)),
+@@ -94,7 +231,7 @@ NativeIOFile::NativeIOFile(
+ }
+ 
+ NativeIOFile::~NativeIOFile() {
+-  // Needed to avoid having the base::File destructor close the file descriptor
++  // Needed to avoid having the FileState destructor close the file descriptor
+   // synchronously on the main thread.
+   CloseBackingFile();
+ }
+@@ -114,6 +251,9 @@ ScriptPromise NativeIOFile::close(ScriptState* script_state) {
+   queued_close_resolver_ = resolver;
+ 
+   if (!io_pending_) {
++    DCHECK(file_state_)
++        << "file_state_ nulled out without setting closed_ or io_pending_";
++
+     // Pretend that a close() promise was queued behind an I/O operation, and
+     // the operation just finished. This is less logic than handling the
+     // non-queued case separately.
+@@ -138,18 +278,15 @@ ScriptPromise NativeIOFile::getLength(ScriptState* script_state,
+                                "The file was already closed"));
+     return ScriptPromise();
+   }
+-  io_pending_ = true;
++  DCHECK(file_state_)
++      << "file_state_ nulled out without setting closed_ or io_pending_";
+ 
++  io_pending_ = true;
+   auto* resolver = MakeGarbageCollected<ScriptPromiseResolver>(script_state);
+-  // CrossThreadUnretained() is safe here because the NativeIOFile::FileState
+-  // instance is owned by this NativeIOFile, which is also passed to the task
+-  // via WrapCrossThreadPersistent. Therefore, the FileState instance is
+-  // guaranteed to remain alive during the task's execution.
+   worker_pool::PostTask(
+       FROM_HERE, {base::MayBlock()},
+       CrossThreadBindOnce(&DoGetLength, WrapCrossThreadPersistent(this),
+-                          WrapCrossThreadPersistent(resolver),
+-                          CrossThreadUnretained(file_state_.get()),
++                          WrapCrossThreadPersistent(resolver), file_state_,
+                           resolver_task_runner_));
+   return resolver->Promise();
+ }
+@@ -175,6 +312,9 @@ ScriptPromise NativeIOFile::setLength(ScriptState* script_state,
+                                "The file was already closed"));
+     return ScriptPromise();
+   }
++  DCHECK(file_state_)
++      << "file_state_ nulled out without setting closed_ or io_pending_";
++
+   int64_t expected_length = base::as_signed(new_length);
+ 
+   DCHECK_GE(expected_length, 0);
+@@ -201,8 +341,8 @@ ScriptPromise NativeIOFile::setLength(ScriptState* script_state,
+     }
+     file_length_ = expected_length;
+   }
+-  io_pending_ = true;
+ 
++  io_pending_ = true;
+   auto* resolver = MakeGarbageCollected<ScriptPromiseResolver>(script_state);
+ 
+ #if defined(OS_MAC)
+@@ -217,26 +357,19 @@ ScriptPromise NativeIOFile::setLength(ScriptState* script_state,
+     // To preserve this invariant, we pass this file's handle to the browser
+     // process during the SetLength() mojo call, and the browser passes it back
+     // when the call completes.
+-    {
+-      WTF::MutexLocker locker(file_state_->mutex);
+-      backend_file_->SetLength(
+-          expected_length, std::move(file_state_->file),
+-          WTF::Bind(&NativeIOFile::DidSetLengthIpc, WrapPersistent(this),
+-                    WrapPersistent(resolver)));
+-    }
++    base::File file = file_state_->TakeFile();
++    backend_file_->SetLength(
++        expected_length, std::move(file),
++        WTF::Bind(&NativeIOFile::DidSetLengthIpc, WrapPersistent(this),
++                  WrapPersistent(resolver)));
+     return resolver->Promise();
+   }
+ #endif  // defined(OS_MAC)
+ 
+-  // CrossThreadUnretained() is safe here because the NativeIOFile::FileState
+-  // instance is owned by this NativeIOFile, which is also passed to the task
+-  // via WrapCrossThreadPersistent. Therefore, the FileState instance is
+-  // guaranteed to remain alive during the task's execution.
+   worker_pool::PostTask(
+       FROM_HERE, {base::MayBlock()},
+       CrossThreadBindOnce(&DoSetLength, WrapCrossThreadPersistent(this),
+-                          WrapCrossThreadPersistent(resolver),
+-                          CrossThreadUnretained(file_state_.get()),
++                          WrapCrossThreadPersistent(resolver), file_state_,
+                           resolver_task_runner_, expected_length));
+   return resolver->Promise();
+ }
+@@ -258,6 +391,8 @@ ScriptPromise NativeIOFile::read(ScriptState* script_state,
+                                "The file was already closed"));
+     return ScriptPromise();
+   }
++  DCHECK(file_state_)
++      << "file_state_ nulled out without setting closed_ or io_pending_";
+ 
+   // TODO(pwnall): This assignment should move right before the
+   // worker_pool::PostTask() call.
+@@ -281,16 +416,10 @@ ScriptPromise NativeIOFile::read(ScriptState* script_state,
+   DCHECK(buffer->IsDetached());
+ 
+   auto* resolver = MakeGarbageCollected<ScriptPromiseResolver>(script_state);
+-  // The first CrossThreadUnretained() is safe here because the
+-  // NativeIOFile::FileState instance is owned by this NativeIOFile, which is
+-  // also passed to the task via WrapCrossThreadPersistent. Therefore, the
+-  // FileState instance is guaranteed to remain alive during the task's
+-  // execution.
+   worker_pool::PostTask(
+       FROM_HERE, {base::MayBlock()},
+       CrossThreadBindOnce(&DoRead, WrapCrossThreadPersistent(this),
+-                          WrapCrossThreadPersistent(resolver),
+-                          CrossThreadUnretained(file_state_.get()),
++                          WrapCrossThreadPersistent(resolver), file_state_,
+                           resolver_task_runner_, std::move(result_buffer_data),
+                           file_offset, read_size));
+   return resolver->Promise();
+@@ -313,6 +442,8 @@ ScriptPromise NativeIOFile::write(ScriptState* script_state,
+                                "The file was already closed"));
+     return ScriptPromise();
+   }
++  DCHECK(file_state_)
++      << "file_state_ nulled out without setting closed_ or io_pending_";
+ 
+   int write_size = NativeIOOperationSize(*buffer);
+   int64_t write_end_offset;
+@@ -346,6 +477,14 @@ ScriptPromise NativeIOFile::write(ScriptState* script_state,
+     file_length_ = write_end_offset;
+   }
+ 
++  // TODO(pwnall): This assignment should move right before the
++  // worker_pool::PostTask() call.
++  //
++  // `io_pending_` should only be set to true when we know for sure we'll post a
++  // task that eventually results in getting `io_pending_` set back to false.
++  // Having `io_pending_` set to true in an early return case (rejecting with an
++  // exception) leaves the NativeIOFile "stuck" in a state where all future I/O
++  // method calls will reject.
+   io_pending_ = true;
+ 
+   std::unique_ptr<NativeIODataBuffer> result_buffer_data =
+@@ -358,16 +497,10 @@ ScriptPromise NativeIOFile::write(ScriptState* script_state,
+   DCHECK(buffer->IsDetached());
+ 
+   auto* resolver = MakeGarbageCollected<ScriptPromiseResolver>(script_state);
+-  // The first CrossThreadUnretained() is safe here because the
+-  // NativeIOFile::FileState instance is owned by this NativeIOFile, which is
+-  // also passed to the task via WrapCrossThreadPersistent. Therefore, the
+-  // FileState instance is guaranteed to remain alive during the task's
+-  // execution.
+   worker_pool::PostTask(
+       FROM_HERE, {base::MayBlock()},
+       CrossThreadBindOnce(&DoWrite, WrapCrossThreadPersistent(this),
+-                          WrapCrossThreadPersistent(resolver),
+-                          CrossThreadUnretained(file_state_.get()),
++                          WrapCrossThreadPersistent(resolver), file_state_,
+                           resolver_task_runner_, std::move(result_buffer_data),
+                           file_offset, write_size));
+   return resolver->Promise();
+@@ -391,18 +524,15 @@ ScriptPromise NativeIOFile::flush(ScriptState* script_state,
+                                "The file was already closed"));
+     return ScriptPromise();
+   }
+-  io_pending_ = true;
++  DCHECK(file_state_)
++      << "file_state_ nulled out without setting closed_ or io_pending_";
+ 
++  io_pending_ = true;
+   auto* resolver = MakeGarbageCollected<ScriptPromiseResolver>(script_state);
+-  // CrossThreadUnretained() is safe here because the NativeIOFile::FileState
+-  // instance is owned by this NativeIOFile, which is also passed to the task
+-  // via WrapCrossThreadPersistent. Therefore, the FileState instance is
+-  // guaranteed to remain alive during the task's execution.
+   worker_pool::PostTask(
+       FROM_HERE, {base::MayBlock()},
+       CrossThreadBindOnce(&DoFlush, WrapCrossThreadPersistent(this),
+-                          WrapCrossThreadPersistent(resolver),
+-                          CrossThreadUnretained(file_state_.get()),
++                          WrapCrossThreadPersistent(resolver), file_state_,
+                           resolver_task_runner_));
+   return resolver->Promise();
+ }
+@@ -430,28 +560,29 @@ void NativeIOFile::DispatchQueuedClose() {
+   ScriptPromiseResolver* resolver = queued_close_resolver_;
+   queued_close_resolver_ = nullptr;
+ 
++  scoped_refptr<FileState> file_state = std::move(file_state_);
++  DCHECK(!file_state_);
++
+   worker_pool::PostTask(
+       FROM_HERE, {base::MayBlock()},
+       CrossThreadBindOnce(&DoClose, WrapCrossThreadPersistent(this),
+                           WrapCrossThreadPersistent(resolver),
+-                          CrossThreadUnretained(file_state_.get()),
+-                          resolver_task_runner_));
++                          std::move(file_state), resolver_task_runner_));
+ }
+ 
+ // static
+ void NativeIOFile::DoClose(
+     CrossThreadPersistent<NativeIOFile> native_io_file,
+     CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-    NativeIOFile::FileState* file_state,
++    scoped_refptr<NativeIOFile::FileState> file_state,
+     scoped_refptr<base::SequencedTaskRunner> resolver_task_runner) {
+   DCHECK(!IsMainThread()) << "File I/O should not happen on the main thread";
++  DCHECK(file_state);
++  DCHECK(file_state->IsValid())
++      << "File I/O operation queued after file closed";
++  DCHECK(resolver_task_runner);
+ 
+-  {
+-    WTF::MutexLocker locker(file_state->mutex);
+-    DCHECK(file_state->file.IsValid())
+-        << "file I/O operation queued after file closed";
+-    file_state->file.Close();
+-  }
++  file_state->Close();
+ 
+   PostCrossThreadTask(
+       *resolver_task_runner, FROM_HERE,
+@@ -482,19 +613,17 @@ void NativeIOFile::DidClose(
+ void NativeIOFile::DoGetLength(
+     CrossThreadPersistent<NativeIOFile> native_io_file,
+     CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-    NativeIOFile::FileState* file_state,
++    scoped_refptr<NativeIOFile::FileState> file_state,
+     scoped_refptr<base::SequencedTaskRunner> resolver_task_runner) {
+   DCHECK(!IsMainThread()) << "File I/O should not happen on the main thread";
++  DCHECK(file_state);
++  DCHECK(file_state->IsValid())
++      << "File I/O operation queued after file closed";
++  DCHECK(resolver_task_runner);
++
++  int64_t length;
+   base::File::Error get_length_error;
+-  int64_t length = -1;
+-  {
+-    WTF::MutexLocker mutex_locker(file_state->mutex);
+-    DCHECK(file_state->file.IsValid())
+-        << "file I/O operation queued after file closed";
+-    length = file_state->file.GetLength();
+-    get_length_error = (length < 0) ? file_state->file.GetLastFileError()
+-                                    : base::File::FILE_OK;
+-  }
++  std::tie(length, get_length_error) = file_state->GetLength();
+ 
+   PostCrossThreadTask(
+       *resolver_task_runner, FROM_HERE,
+@@ -541,22 +670,20 @@ void NativeIOFile::DidGetLength(
+ void NativeIOFile::DoSetLength(
+     CrossThreadPersistent<NativeIOFile> native_io_file,
+     CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-    NativeIOFile::FileState* file_state,
++    scoped_refptr<NativeIOFile::FileState> file_state,
+     scoped_refptr<base::SequencedTaskRunner> resolver_task_runner,
+     int64_t expected_length) {
+   DCHECK(!IsMainThread()) << "File I/O should not happen on the main thread";
++  DCHECK(file_state);
++  DCHECK(file_state->IsValid())
++      << "File I/O operation queued after file closed";
++  DCHECK(resolver_task_runner);
++  DCHECK_GE(expected_length, 0);
+ 
+-  base::File::Error set_length_error;
+   int64_t actual_length;
+-  {
+-    WTF::MutexLocker mutex_locker(file_state->mutex);
+-    DCHECK(file_state->file.IsValid())
+-        << "file I/O operation queued after file closed";
+-    bool success = file_state->file.SetLength(expected_length);
+-    set_length_error =
+-        success ? base::File::FILE_OK : file_state->file.GetLastFileError();
+-    actual_length = success ? expected_length : file_state->file.GetLength();
+-  }
++  base::File::Error set_length_error;
++  std::tie(actual_length, set_length_error) =
++      file_state->SetLength(expected_length);
+ 
+   PostCrossThreadTask(
+       *resolver_task_runner, FROM_HERE,
+@@ -619,10 +746,7 @@ void NativeIOFile::DidSetLengthIpc(
+     int64_t actual_length,
+     mojom::blink::NativeIOErrorPtr set_length_error) {
+   DCHECK(backing_file.IsValid()) << "browser returned closed file";
+-  {
+-    WTF::MutexLocker locker(file_state_->mutex);
+-    file_state_->file = std::move(backing_file);
+-  }
++  file_state_->SetFile(std::move(backing_file));
+   ScriptState* script_state = resolver->GetScriptState();
+ 
+   DCHECK(io_pending_) << "I/O operation performed without io_pending_ set";
+@@ -673,13 +797,15 @@ void NativeIOFile::DidSetLengthIpc(
+ void NativeIOFile::DoRead(
+     CrossThreadPersistent<NativeIOFile> native_io_file,
+     CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-    NativeIOFile::FileState* file_state,
++    scoped_refptr<NativeIOFile::FileState> file_state,
+     scoped_refptr<base::SequencedTaskRunner> resolver_task_runner,
+     std::unique_ptr<NativeIODataBuffer> result_buffer_data,
+     uint64_t file_offset,
+     int read_size) {
+   DCHECK(!IsMainThread()) << "File I/O should not happen on the main thread";
+-
++  DCHECK(file_state);
++  DCHECK(file_state->IsValid())
++      << "File I/O operation queued after file closed";
+   DCHECK(resolver_task_runner);
+   DCHECK(result_buffer_data);
+   DCHECK(result_buffer_data->IsValid());
+@@ -690,15 +816,8 @@ void NativeIOFile::DoRead(
+ 
+   int read_bytes;
+   base::File::Error read_error;
+-  {
+-    WTF::MutexLocker mutex_locker(file_state->mutex);
+-    DCHECK(file_state->file.IsValid())
+-        << "file I/O operation queued after file closed";
+-    read_bytes = file_state->file.Read(file_offset, result_buffer_data->Data(),
+-                                       read_size);
+-    read_error = (read_bytes < 0) ? file_state->file.GetLastFileError()
+-                                  : base::File::FILE_OK;
+-  }
++  std::tie(read_bytes, read_error) =
++      file_state->Read(result_buffer_data.get(), file_offset, read_size);
+ 
+   PostCrossThreadTask(
+       *resolver_task_runner, FROM_HERE,
+@@ -743,12 +862,15 @@ void NativeIOFile::DidRead(
+ void NativeIOFile::DoWrite(
+     CrossThreadPersistent<NativeIOFile> native_io_file,
+     CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-    NativeIOFile::FileState* file_state,
++    scoped_refptr<NativeIOFile::FileState> file_state,
+     scoped_refptr<base::SequencedTaskRunner> resolver_task_runner,
+     std::unique_ptr<NativeIODataBuffer> result_buffer_data,
+     uint64_t file_offset,
+     int write_size) {
+   DCHECK(!IsMainThread()) << "File I/O should not happen on the main thread";
++  DCHECK(file_state);
++  DCHECK(file_state->IsValid())
++      << "File I/O operation queued after file closed";
+   DCHECK(resolver_task_runner);
+   DCHECK(result_buffer_data);
+   DCHECK(result_buffer_data->IsValid());
+@@ -760,22 +882,8 @@ void NativeIOFile::DoWrite(
+   int written_bytes;
+   int64_t actual_file_length_on_failure = 0;
+   base::File::Error write_error;
+-  {
+-    WTF::MutexLocker mutex_locker(file_state->mutex);
+-    DCHECK(file_state->file.IsValid())
+-        << "file I/O operation queued after file closed";
+-    written_bytes = file_state->file.Write(
+-        file_offset, result_buffer_data->Data(), write_size);
+-    write_error = (written_bytes < 0) ? file_state->file.GetLastFileError()
+-                                      : base::File::FILE_OK;
+-    if (written_bytes < write_size || write_error != base::File::FILE_OK) {
+-      actual_file_length_on_failure = file_state->file.GetLength();
+-      if (actual_file_length_on_failure < 0 &&
+-          write_error != base::File::FILE_OK) {
+-        write_error = file_state->file.GetLastFileError();
+-      }
+-    }
+-  }
++  std::tie(actual_file_length_on_failure, written_bytes, write_error) =
++      file_state->Write(result_buffer_data.get(), file_offset, write_size);
+ 
+   PostCrossThreadTask(
+       *resolver_task_runner, FROM_HERE,
+@@ -846,18 +954,14 @@ void NativeIOFile::DidWrite(
+ void NativeIOFile::DoFlush(
+     CrossThreadPersistent<NativeIOFile> native_io_file,
+     CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-    NativeIOFile::FileState* file_state,
++    scoped_refptr<NativeIOFile::FileState> file_state,
+     scoped_refptr<base::SequencedTaskRunner> resolver_task_runner) {
+   DCHECK(!IsMainThread()) << "File I/O should not happen on the main thread";
+-  base::File::Error flush_error;
+-  {
+-    WTF::MutexLocker mutex_locker(file_state->mutex);
+-    DCHECK(file_state->file.IsValid())
+-        << "file I/O operation queued after file closed";
+-    bool success = file_state->file.Flush();
+-    flush_error =
+-        success ? base::File::FILE_OK : file_state->file.GetLastFileError();
+-  }
++  DCHECK(file_state);
++  DCHECK(file_state->IsValid())
++      << "File I/O operation queued after file closed";
++
++  base::File::Error flush_error = file_state->Flush();
+ 
+   PostCrossThreadTask(
+       *resolver_task_runner, FROM_HERE,
+@@ -887,20 +991,23 @@ void NativeIOFile::DidFlush(
+ 
+ void NativeIOFile::CloseBackingFile() {
+   closed_ = true;
+-  file_state_->mutex.lock();
+-  base::File backing_file = std::move(file_state_->file);
+-  file_state_->mutex.unlock();
+ 
+-  if (!backing_file.IsValid()) {
++  if (!file_state_) {
+     // Avoid posting a cross-thread task if the file is already closed. This is
+     // the expected path.
+     return;
+   }
+ 
+-  worker_pool::PostTask(
+-      FROM_HERE, {base::MayBlock()},
+-      CrossThreadBindOnce([](base::File file) { file.Close(); },
+-                          std::move(backing_file)));
++  scoped_refptr<FileState> file_state = std::move(file_state_);
++  DCHECK(!file_state_);
++
++  worker_pool::PostTask(FROM_HERE, {base::MayBlock()},
++                        CrossThreadBindOnce(
++                            [](scoped_refptr<FileState> file_state) {
++                              DCHECK(file_state);
++                              file_state->Close();
++                            },
++                            std::move(file_state)));
+ }
+ 
+ }  // namespace blink
+diff --git a/third_party/blink/renderer/modules/native_io/native_io_file.h b/third_party/blink/renderer/modules/native_io/native_io_file.h
+index 8ae49ebc2d36d547d152d4e56192e30f8cacd641..95d2da4ac3e1859a0abc21ea15d269758eed1681 100644
+--- a/third_party/blink/renderer/modules/native_io/native_io_file.h
++++ b/third_party/blink/renderer/modules/native_io/native_io_file.h
+@@ -67,12 +67,7 @@ class NativeIOFile final : public ScriptWrappable {
+   void Trace(Visitor* visitor) const override;
+ 
+  private:
+-  // Data accessed on the threads that do file I/O.
+-  //
+-  // Instances are allocated on the PartitionAlloc heap. Instances are initially
+-  // constructed on Blink's main thread, or on a worker thread. Afterwards,
+-  // instances are only accessed on dedicated threads that do blocking file I/O.
+-  struct FileState;
++  class FileState;
+ 
+   // Called when the mojo backend disconnects.
+   void OnBackendDisconnect();
+@@ -84,7 +79,7 @@ class NativeIOFile final : public ScriptWrappable {
+   static void DoClose(
+       CrossThreadPersistent<NativeIOFile> native_io_file,
+       CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-      NativeIOFile::FileState* file_state,
++      scoped_refptr<NativeIOFile::FileState> file_state,
+       scoped_refptr<base::SequencedTaskRunner> file_task_runner);
+   // Performs the post file I/O part of close(), on the main thread.
+   void DidClose(CrossThreadPersistent<ScriptPromiseResolver> resolver);
+@@ -93,7 +88,7 @@ class NativeIOFile final : public ScriptWrappable {
+   static void DoGetLength(
+       CrossThreadPersistent<NativeIOFile> native_io_file,
+       CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-      NativeIOFile::FileState* file_state,
++      scoped_refptr<NativeIOFile::FileState> file_state,
+       scoped_refptr<base::SequencedTaskRunner> file_task_runner);
+   // Performs the post file I/O part of getLength(), on the main thread.
+   void DidGetLength(CrossThreadPersistent<ScriptPromiseResolver> resolver,
+@@ -104,7 +99,7 @@ class NativeIOFile final : public ScriptWrappable {
+   static void DoSetLength(
+       CrossThreadPersistent<NativeIOFile> native_io_file,
+       CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-      NativeIOFile::FileState* file_state,
++      scoped_refptr<NativeIOFile::FileState> file_state,
+       scoped_refptr<base::SequencedTaskRunner> file_task_runner,
+       int64_t expected_length);
+   // Performs the post file I/O part of setLength(), on the main thread.
+@@ -128,7 +123,7 @@ class NativeIOFile final : public ScriptWrappable {
+   // Performs the file I/O part of read(), off the main thread.
+   static void DoRead(CrossThreadPersistent<NativeIOFile> native_io_file,
+                      CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-                     NativeIOFile::FileState* file_state,
++                     scoped_refptr<NativeIOFile::FileState> file_state,
+                      scoped_refptr<base::SequencedTaskRunner> file_task_runner,
+                      std::unique_ptr<NativeIODataBuffer> result_buffer_data,
+                      uint64_t file_offset,
+@@ -143,7 +138,7 @@ class NativeIOFile final : public ScriptWrappable {
+   static void DoWrite(
+       CrossThreadPersistent<NativeIOFile> native_io_file,
+       CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-      NativeIOFile::FileState* file_state,
++      scoped_refptr<NativeIOFile::FileState> file_state,
+       scoped_refptr<base::SequencedTaskRunner> resolver_task_runner,
+       std::unique_ptr<NativeIODataBuffer> result_buffer_data,
+       uint64_t file_offset,
+@@ -163,7 +158,7 @@ class NativeIOFile final : public ScriptWrappable {
+   static void DoFlush(
+       CrossThreadPersistent<NativeIOFile> native_io_file,
+       CrossThreadPersistent<ScriptPromiseResolver> resolver,
+-      NativeIOFile::FileState* file_state,
++      scoped_refptr<NativeIOFile::FileState> file_state,
+       scoped_refptr<base::SequencedTaskRunner> file_task_runner);
+   // Performs the post file-I/O part of flush(), on the main thread.
+   void DidFlush(CrossThreadPersistent<ScriptPromiseResolver> resolver,
+@@ -210,8 +205,13 @@ class NativeIOFile final : public ScriptWrappable {
+   // TODO(rstz): Consider moving this variable into `file_state_`
+   int64_t file_length_ = 0;
+ 
+-  // See NativeIOFile::FileState, declared above.
+-  const std::unique_ptr<FileState> file_state_;
++  // Points to a NativeIOFile::FileState while the underlying file is open.
++  //
++  // When the underlying file is closed, this pointer is nulled out, and the
++  // FileState instance is passed to a different thread, where the closing
++  // happens. This avoids having any I/O performed by the base::File::Close()
++  // jank the JavaScript thread that owns this NativeIOFile instance.
++  scoped_refptr<FileState> file_state_;
+ 
+   // Schedules resolving Promises with file I/O results.
+   const scoped_refptr<base::SequencedTaskRunner> resolver_task_runner_;