cc: Check for cheap task completion sooner

cc/worker_pool.cc

 // 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.
 
 #include "cc/worker_pool.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
@@ skipping 373 matching lines @@
       break;
     }
   }
 
   // Defer remaining tasks to worker threads.
   while (pending_cheap_tasks_.size()) {
     scoped_ptr<internal::WorkerPoolTask> task =
         pending_cheap_tasks_.take_front();
     PostTask(task.Pass(), false);
   }
+
   run_cheap_tasks_pending_ = false;
+  if (base::subtle::Acquire_Load(&pending_task_count_) == 0)
+    OnIdle();
 }
 
 }  // namespace cc