7000847: add type tag to v8::External for gin_helper function templates

The upstream gin function templates now use v8::ExternalPointerTypeTag
for type safety when using v8::External. Updated Electron's forked
gin_helper function template to use the same kGinInternalCallbackHolderBaseTag
that Chromium's gin uses.

Ref: https://chromium-review.googlesource.com/c/chromium/src/+/7000847

shell/common/gin_helper/function_template.cc

@@ -5,6 +5,7 @@
 #include "shell/common/gin_helper/function_template.h"
 
 #include "base/strings/strcat.h"
+#include "gin/public/gin_embedders.h"
 
 namespace gin_helper {
 
@@ -29,7 +30,10 @@ void CallbackHolderBase::DisposeObserver::OnDisposed() {
 }
 
 CallbackHolderBase::CallbackHolderBase(v8::Isolate* isolate)
-    : v8_ref_(isolate, v8::External::New(isolate, this)),
+    : v8_ref_(isolate,
+              v8::External::New(isolate,
+                                this,
+                                gin::kGinInternalCallbackHolderBaseTag)),
       dispose_observer_(gin::PerIsolateData::From(isolate), this) {
   v8_ref_.SetWeak(this, &CallbackHolderBase::FirstWeakCallback,
                   v8::WeakCallbackType::kParameter);

shell/common/gin_helper/function_template.h

@@ -13,6 +13,7 @@
 #include "base/memory/raw_ptr.h"
 #include "gin/arguments.h"
 #include "gin/per_isolate_data.h"
+#include "gin/public/gin_embedders.h"
 #include "shell/common/gin_helper/destroyable.h"
 #include "shell/common/gin_helper/error_thrower.h"
 #include "v8/include/v8-context.h"
@@ -289,8 +290,8 @@ struct Dispatcher<ReturnType(ArgTypes...)> {
   static void DispatchToCallbackImpl(gin::Arguments* args) {
     v8::Local<v8::External> v8_holder;
     CHECK(args->GetData(&v8_holder));
-    CallbackHolderBase* holder_base =
-        reinterpret_cast<CallbackHolderBase*>(v8_holder->Value());
+    CallbackHolderBase* holder_base = reinterpret_cast<CallbackHolderBase*>(
+        v8_holder->Value(gin::kGinInternalCallbackHolderBaseTag));
 
     typedef CallbackHolder<ReturnType(ArgTypes...)> HolderT;
     HolderT* holder = static_cast<HolderT*>(holder_base);