Add support for Low Priorirty tasks.

public/platform/WebSchedulerProxy.h

 // 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.
 
 #ifndef WebSchedulerProxy_h
 #define WebSchedulerProxy_h
 
 #include "WebThread.h"
 
 namespace blink {
 
 class Scheduler;
 class WebTraceLocation;
 
 // This class is used to submit tasks to Blink's main thread scheduler.
 class WebSchedulerProxy {
 public:
     BLINK_PLATFORM_EXPORT ~WebSchedulerProxy();
 
     BLINK_PLATFORM_EXPORT static WebSchedulerProxy create();
 
     // Schedule an input processing task to be run on the Blink main thread.
     // Takes ownership of |Task|. Can be called from any thread.
     BLINK_PLATFORM_EXPORT void postInputTask(const WebTraceLocation&, WebThread::Task*);
 
     // Schedule a compositor task to run on the Blink main thread. Takes
     // ownership of |Task|. Can be called from any thread.
     BLINK_PLATFORM_EXPORT void postCompositorTask(const WebTraceLocation&, WebThread::Task*);
 
+    // Schedule a task due to an IPC to be run on the Blink main thread.
+    // Takes ownership of |Task|. Can be called from any thread.
+    BLINK_PLATFORM_EXPORT void postIpcTask(const WebTraceLocation&, WebThread::Task*);
+
 private:
     WebSchedulerProxy();
 
     Scheduler* m_scheduler;
 };
 
 } // namespace blink
 
 #endif // WebSchedulerProxy_h