[Reland] Post loading tasks on the appropriate WebFrameScheduler's queue

third_party/WebKit/public/platform/WebTaskRunner.h

 // Copyright 2015 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 WebTaskRunner_h
 #define WebTaskRunner_h
 
 #include "WebCommon.h"
 
 #ifdef INSIDE_BLINK
@@ skipping 10 matching lines @@
     virtual ~WebTaskRunner() {}
 
     class BLINK_PLATFORM_EXPORT Task {
     public:
         virtual ~Task() { }
         virtual void run() = 0;
     };
 
     // Schedule a task to be run on the the associated WebThread.
     // Takes ownership of |Task|. Can be called from any thread.
-    virtual void postTask(const WebTraceLocation&, Task*) {}
+    virtual void postTask(const WebTraceLocation&, Task*) = 0;
 
     // Schedule a task to be run after |delayMs| on the the associated WebThread.
     // Takes ownership of |Task|. Can be called from any thread.
-    virtual void postDelayedTask(const WebTraceLocation&, Task*, double delayMs) {}
+    virtual void postDelayedTask(const WebTraceLocation&, Task*, double delayMs) = 0;
+
+    // Returns a clone of the WebTaskRunner.
+    virtual WebTaskRunner* clone() = 0;
 
 #ifdef INSIDE_BLINK
     // Helpers for posting bound functions as tasks.
     typedef Function<void()> ClosureTask;
 
     void postTask(const WebTraceLocation&, PassOwnPtr<ClosureTask>);
     // TODO(alexclarke): Remove this when possible.
     void postDelayedTask(const WebTraceLocation&, PassOwnPtr<ClosureTask>, long long delayMs);
     void postDelayedTask(const WebTraceLocation&, PassOwnPtr<ClosureTask>, double delayMs);
 #endif
 };
 
 } // namespace blink
 
 #endif // WebTaskRunner_h