fix: correctly handle nexttick scheduling in stream reads (#24081)

Co-authored-by: Paul Frazee <pfrazee@gmail.com>

shell/browser/net/node_stream_loader.cc

@@ -68,6 +68,8 @@ void NodeStreamLoader::Start(network::mojom::URLResponseHeadPtr head) {
 void NodeStreamLoader::NotifyReadable() {
   if (!readable_)
     ReadMore();
+  else if (is_reading_)
+    has_read_waiting_ = true;
   readable_ = true;
 }
 
@@ -101,8 +103,16 @@ void NodeStreamLoader::ReadMore() {
   // If there is no buffer read, wait until |readable| is emitted again.
   v8::Local<v8::Value> buffer;
   if (!ret.ToLocal(&buffer) || !node::Buffer::HasInstance(buffer)) {
-    readable_ = false;
     is_reading_ = false;
+
+    // If 'readable' was called after 'read()', try again
+    if (has_read_waiting_) {
+      has_read_waiting_ = false;
+      ReadMore();
+      return;
+    }
+
+    readable_ = false;
     if (ended_) {
       NotifyComplete(result_);
     }

shell/browser/net/node_stream_loader.h

@@ -87,6 +87,11 @@ class NodeStreamLoader : public network::mojom::URLLoader {
   // flag.
   bool readable_ = false;
 
+  // It's possible for reads to be queued using nextTick() during read()
+  // which will cause 'readable' to emit during ReadMore, so we track if
+  // that occurred in a flag.
+  bool has_read_waiting_ = false;
+
   // Store the V8 callbacks to unsubscribe them later.
   std::map<std::string, v8::Global<v8::Value>> handlers_;