Refactor TimeBase to post tasks. Workers to use real Idle tasks.

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"
 
@@ skipping 46 matching lines @@
     // 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*) { }
 
     // Schedule a timer task to be run on the the associated WebThread. Timer Tasks
     // tasks usually have the default priority, but may be delayed
     // when the user is interacting with the device.
     // Takes ownership of |WebThread::Task|. Can be called from any thread.
     virtual void postTimerTask(const WebTraceLocation&, WebThread::Task*, long long delayMs) { }
 
+    // Schedule a shutdown task to be run on the the associated WebThread. Shutdown
+    // tasks can run at any time, including after preShutdown has been called.
+    // Takes ownership of |WebThread::Task|. Can be called from any thread.
+    virtual void postShutdownTask(const WebTraceLocation&, WebThread::Task*, long long delayMs) { }
+
+    // Prevents execution of all tasks posted vis this interface, except shutdown tasks.
+    virtual void preShutdown() { }
+
 #ifdef INSIDE_BLINK
     // Helpers for posting bound functions as tasks.
-    typedef Function<void(double deadlineSeconds)> IdleTask;
-    typedef Function<void()> Task;
+    typedef WTF::Function<void(double deadlineSeconds)> IdleTask;
+    typedef WTF::Function<void()> Task;
 
     void postIdleTask(const WebTraceLocation&, PassOwnPtr<IdleTask>);
     void postNonNestableIdleTask(const WebTraceLocation&, PassOwnPtr<IdleTask>);
     void postIdleTaskAfterWakeup(const WebTraceLocation&, PassOwnPtr<IdleTask>);
     void postLoadingTask(const WebTraceLocation&, PassOwnPtr<Task>);
 #endif
 };
 
 } // namespace blink
 
 #endif // WebScheduler_h