WebThreadImplForMessageLoop to use blink scheduler

content/child/blink_platform_impl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/child/blink_platform_impl.h"
 
 #include <math.h>
 
 #include <vector>
 
@@ skipping 399 matching lines @@
     // This "default:" line exists to avoid compile warnings about enum
     // coverage when we add a new symbol to WebLocalizedString.h in WebKit.
     // After a planned WebKit patch is landed, we need to add a case statement
     // for the added symbol here.
     default:
       break;
   }
   return -1;
 }
 
 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),
       shared_timer_suspended_(0),
       current_thread_slot_(&DestroyCurrentThread) {
   // ChildThread may not exist in some tests.
   if (ChildThread::current()) {
     geofencing_provider_.reset(new WebGeofencingProviderImpl(
         ChildThread::current()->thread_safe_sender()));
     thread_safe_sender_ = ChildThread::current()->thread_safe_sender();
@@ skipping 51 matching lines @@
 blink::WebThread* BlinkPlatformImpl::createThread(const char* name) {
   return new WebThreadImpl(name);
 }
 
 blink::WebThread* BlinkPlatformImpl::currentThread() {
   WebThreadImplForMessageLoop* thread =
       static_cast<WebThreadImplForMessageLoop*>(current_thread_slot_.Get());
   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;
 }
 
 void BlinkPlatformImpl::yieldCurrentThread() {
   base::PlatformThread::YieldCurrentThread();
 }
 
 blink::WebWaitableEvent* BlinkPlatformImpl::createWaitableEvent() {
   return new WebWaitableEventImpl();
@@ skipping 476 matching lines @@
                       this, &BlinkPlatformImpl::DoTimeout);
   OnStartSharedTimer(base::TimeDelta::FromMicroseconds(interval));
 }
 
 void BlinkPlatformImpl::stopSharedTimer() {
   shared_timer_.Stop();
 }
 
 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(
     blink::WebGestureDevice device_source,
     const blink::WebFloatPoint& velocity,
     const blink::WebSize& cumulative_scroll) {
   auto curve = WebGestureCurveImpl::CreateFromDefaultPlatformCurve(
       gfx::Vector2dF(velocity.x, velocity.y),
       gfx::Vector2dF(cumulative_scroll.width, cumulative_scroll.height));
   return curve.release();
@@ skipping 208 matching lines @@
 }
 
 // static
 void BlinkPlatformImpl::DestroyCurrentThread(void* thread) {
   WebThreadImplForMessageLoop* impl =
       static_cast<WebThreadImplForMessageLoop*>(thread);
   delete impl;
 }
 
 }  // namespace content