WebThreadImplForMessageLoop to use blink scheduler

content/child/blink_platform_impl.cc

Index: content/child/blink_platform_impl.cc
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index 79f72adcffcbe5daa58d9d36e8d9587f52cc11ce..a05fea4538ae497d9631510fc0a789bab2528684 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -418,7 +418,7 @@ static int ToMessageID(WebLocalizedString::Name name) {
 }
 
 BlinkPlatformImpl::BlinkPlatformImpl()

[Sami, 2014/11/04 01:59:01]

Could we make main_thread_task_runner a parameter here? This constructor might
end up passing it to other things before the derived class replaces it with the
correct one.

[alex clarke (OOO till 29th), 2014/11/04 18:40:20]

I've added a new constructor rather than altering all the existing ones since
that would make the patch significantly larger.

-    : main_loop_(base::MessageLoop::current()),
+    : main_thread_task_runner_(base::MessageLoopProxy::current()),
       shared_timer_func_(NULL),
       shared_timer_fire_time_(0.0),
       shared_timer_fire_time_was_set_while_suspended_(false),
@@ -490,12 +490,17 @@ blink::WebThread* BlinkPlatformImpl::currentThread() {
   if (thread)
     return (thread);
 
-  scoped_refptr<base::MessageLoopProxy> message_loop =
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner =
       base::MessageLoopProxy::current();
-  if (!message_loop.get())
+  if (main_thread_task_runner_.get() &&

[Sami, 2014/11/04 01:59:01]

|main_thread_task_runner_| should always be non-null. IMO this would read a
little easier like this:

  scoped_refptr<base::SingleThreadTaskRunner> task_runner;
  if (main_thread_task_runner_->BelongsToCurrentThread()) {
    task_runner = main_thread_task_runner_;
  } else {
    task_runner = base::MessageLoopProxy::current();
  }

[alex clarke (OOO till 29th), 2014/11/04 18:40:20]

That's not always true and in fact the browser will crash on startup if we
assume this.

+      main_thread_task_runner_->BelongsToCurrentThread()) {
+    task_runner = main_thread_task_runner_;
+  }
+
+  if (!task_runner.get())
     return NULL;
 
-  thread = new WebThreadImplForMessageLoop(message_loop.get());
+  thread = new WebThreadImplForMessageLoop(task_runner);
   current_thread_slot_.Set(thread);
   return thread;
 }
@@ -992,7 +997,7 @@ void BlinkPlatformImpl::stopSharedTimer() {
 
 void BlinkPlatformImpl::callOnMainThread(
     void (*func)(void*), void* context) {
-  main_loop_->PostTask(FROM_HERE, base::Bind(func, context));
+  main_thread_task_runner_->PostTask(FROM_HERE, base::Bind(func, context));
 }
 
 blink::WebGestureCurve* BlinkPlatformImpl::createFlingAnimationCurve(