cc: BlockingTaskRunner without MessageLoopProxy

cc/trees/proxy.cc

 // Copyright 2011 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 "cc/trees/proxy.h"
 
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/single_thread_task_runner.h"
 
 namespace cc {
 
 base::SingleThreadTaskRunner* Proxy::MainThreadTaskRunner() const {
   return main_task_runner_.get();
 }
 
 bool Proxy::HasImplThread() const { return !!impl_task_runner_.get(); }
 
 base::SingleThreadTaskRunner* Proxy::ImplThreadTaskRunner() const {
   return impl_task_runner_.get();
 }
 
 bool Proxy::IsMainThread() const {
 #if DCHECK_IS_ON
-  DCHECK(main_task_runner_.get());
   if (impl_thread_is_overridden_)
     return false;
-  return main_task_runner_->BelongsToCurrentThread();
+
+  bool is_main_thread = base::PlatformThread::CurrentId() == main_thread_id_;
+  if (is_main_thread && main_task_runner_.get()) {
+    DCHECK(main_task_runner_->BelongsToCurrentThread());
+  }
+  return is_main_thread;
 #else
   return true;
 #endif
 }
 
 bool Proxy::IsImplThread() const {
 #if DCHECK_IS_ON
   if (impl_thread_is_overridden_)
     return true;
   if (!impl_task_runner_.get())
@@ skipping 23 matching lines @@
   is_main_thread_blocked_ = is_main_thread_blocked;
 }
 #endif
 
 Proxy::Proxy(scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner)
     : main_task_runner_(base::MessageLoopProxy::current()),
 #if !DCHECK_IS_ON
       impl_task_runner_(impl_task_runner) {
 #else
       impl_task_runner_(impl_task_runner),
+      main_thread_id_(base::PlatformThread::CurrentId()),
       impl_thread_is_overridden_(false),
       is_main_thread_blocked_(false) {
 #endif
 }
 
 Proxy::~Proxy() {
   DCHECK(IsMainThread());
 }
 
 scoped_ptr<base::Value> Proxy::SchedulerAsValueForTesting() {
   return make_scoped_ptr(base::Value::CreateNullValue());
 }
 
 }  // namespace cc