Remove WebScheduler::shutdown() which is no longer needed.

public/platform/WebScheduler.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 WebScheduler_h
 #define WebScheduler_h
 
 #include "WebCommon.h"
 #include "public/platform/WebThread.h"
 
 namespace blink {
 
 class WebTraceLocation;
 
 // This class is used to submit tasks and pass other information from Blink to
 // the platform's scheduler.
 class BLINK_PLATFORM_EXPORT WebScheduler {
 public:
     virtual ~WebScheduler() { }
 
     // An IdleTask is passed a deadline in CLOCK_MONOTONIC seconds and is
     // expected to complete before this deadline.
     class IdleTask {
     public:
         virtual ~IdleTask() { }
         virtual void run(double deadlineSeconds) = 0;
     };
 
-    // Called during Blink's shutdown to delete any pending tasks from the
-    // scheduler. Must be called on the main thread.
-    virtual void shutdown() { }
-
     // Returns true if there is high priority work pending on the main thread
     // and the caller should yield to let the scheduler service that work.
     // Must be called on the main thread.
     virtual bool shouldYieldForHighPriorityWork() { return false; }
 
     // Schedule an idle task to run the Blink main thread. For non-critical
     // tasks which may be reordered relative to other task types and may be
     // starved for an arbitrarily long time if no idle time is available.
     // Takes ownership of |IdleTask|. Can be called from any thread.
     virtual void postIdleTask(const WebTraceLocation&, IdleTask*) { }
@@ skipping 14 matching lines @@
     // Schedule a loading task to be run on the Blink main thread. Loading
     // tasks usually have the default priority, but may be deprioritised
     // when the user is interacting with the device.
     // Takes ownership of |WebThread::Task|. Can be called from any thread.
     virtual void postLoadingTask(const WebTraceLocation&, WebThread::Task*) { }
 };
 
 } // namespace blink
 
 #endif // WebScheduler_h