cc: Use correct message loop proxy in BlockingTaskRunner

cc/trees/blocking_task_runner.h

 // Copyright 2013 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.
 
 #ifndef CC_TREES_BLOCKING_TASK_RUNNER_H_
 #define CC_TREES_BLOCKING_TASK_RUNNER_H_
 
 #include <vector>
 
 #include "base/location.h"
@@ skipping 54 matching lines @@
   // thread.
   bool BelongsToCurrentThread();
 
   // Posts a task using the contained SingleThreadTaskRunner unless |capture_|
   // is true. When |capture_| is true, tasks posted will be caught and stored
   // until the capturing stops. At that time the tasks will be run directly
   // instead of being posted to the SingleThreadTaskRunner.
   bool PostTask(const tracked_objects::Location& from_here,
                 const base::Closure& task);
 
+  // Forward the tasks to a specific task runner instead of the

[danakj, 2014/08/26 15:59:00]

WDYT of passing this to current() and DCHECKing that it matches the existing
BlockingTaskRunner if one already exists?

Would the changes to Proxy no longer be needed?

[Sami, 2014/08/26 16:19:17]

The places[1] that call BlockingTaskRunner::current() don't have an easy way to
access the main_task_runner_ from Proxy :( Or did you mean something like the
runner only needs to be passed in the first time this is called and after that
it sticks?

[1] DelegatedFrameResourceCollection, DelegatedRendererLayer and TextureLayer

+  // MessageLoopProxy which was current when this task runner was constructed.
+  // Must not be called while capturing tasks.
+  void SetTaskRunner(scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+
  private:
   friend class base::RefCountedThreadSafe<BlockingTaskRunner>;
 
   explicit BlockingTaskRunner(
       scoped_refptr<base::SingleThreadTaskRunner> task_runner);
   virtual ~BlockingTaskRunner();
 
   void SetCapture(bool capture);
 
   base::PlatformThreadId thread_id_;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   base::Lock lock_;
   int capture_;
   std::vector<base::Closure> captured_tasks_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_BLOCKING_TASK_RUNNER_H_