Purge memory before suspending timer queues when backgrounded.

third_party/WebKit/public/platform/Platform.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 651 matching lines @@
   virtual WebPushProvider* pushProvider() { return nullptr; }
 
   // Background Sync API-------------------------------------------------
 
   virtual WebSyncProvider* backgroundSyncProvider() { return nullptr; }
 
   // Experimental Framework ----------------------------------------------
 
   virtual WebTrialTokenValidator* trialTokenValidator() { return nullptr; }
 
+  // Memory ------------------------------------------------------------
+
+  // Requests purging memory. The platform may or may not purge memory,
+  // depending on memory pressure.
+  virtual void requestPurgeMemory() {}
+
  protected:
   Platform();
   virtual ~Platform() {}
 
   WebThread* m_mainThread;
 };
 
 }  // namespace blink
 
 #endif