Add setBatteryListener into Platform.

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 37 matching lines @@
 #include "WebStorageQuotaType.h"
 #include "WebString.h"
 #include "WebURLError.h"
 #include "WebVector.h"
 
 class GrContext;
 
 namespace blink {
 
 class WebAudioBus;
+class WebBatteryStatusListener;
 class WebBlobRegistry;
 class WebContentDecryptionModule;
 class WebClipboard;
 class WebCompositorSupport;
 class WebConvertableToTraceFormat;
 class WebCookieJar;
 class WebCrypto;
 class WebDatabaseObserver;
 class WebDeviceMotionListener;
 class WebDeviceOrientationListener;
@@ skipping 85 matching lines @@
     virtual WebAudioDevice* createAudioDevice(size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfChannels, double sampleRate, WebAudioDevice::RenderCallback*, const WebString& deviceId) { return 0; }
 
 
     // MIDI ----------------------------------------------------------------
 
     // Creates a platform dependent WebMIDIAccessor. MIDIAccessor under platform
     // creates and owns it.
     virtual WebMIDIAccessor* createMIDIAccessor(WebMIDIAccessorClient*) { return 0; }
 
 
+    // Battery -------------------------------------------------------------
+
+    // Sets the listener for watching battery status updates.
+    virtual void setBatteryStatusListener(blink::WebBatteryStatusListener*) { }
+
+
     // Blob ----------------------------------------------------------------
 
     // Must return non-null.
     virtual WebBlobRegistry* blobRegistry() { return 0; }
 
 
     // Database ------------------------------------------------------------
 
     // Opens a database file; dirHandle should be 0 if the caller does not need
     // a handle to the directory containing this file
@@ skipping 469 matching lines @@
     virtual WebDatabaseObserver* databaseObserver() { return 0; }
 
 
 protected:
     virtual ~Platform() { }
 };
 
 } // namespace blink
 
 #endif