Remove OnThemeChanged and associated unused message

content/renderer/render_view_impl.h

 // Copyright (c) 2012 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 CONTENT_RENDERER_RENDER_VIEW_IMPL_H_
 #define CONTENT_RENDERER_RENDER_VIEW_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 607 matching lines @@
   void OnSetActive(bool active);
   void OnSetBackgroundOpaque(bool opaque);
   void OnExitFullscreen();
   void OnSetHistoryOffsetAndLength(int history_offset, int history_length);
   void OnSetInitialFocus(bool reverse);
   void OnSetPageEncoding(const std::string& encoding_name);
   void OnSetRendererPrefs(const RendererPreferences& renderer_prefs);
   void OnSetWebUIProperty(const std::string& name, const std::string& value);
   void OnSetZoomLevelForLoadingURL(const GURL& url, double zoom_level);
   void OnSuppressDialogsUntilSwapOut();
-  void OnThemeChanged();
   void OnUpdateTargetURLAck();
   void OnUpdateWebPreferences(const WebPreferences& prefs);
   void OnSetPageScale(float page_scale_factor);
   void OnZoom(PageZoom zoom);
   void OnForceRedraw(const ui::LatencyInfo& latency_info);
   void OnSelectWordAroundCaret();
 #if defined(OS_ANDROID)
   void OnUndoScrollFocusedEditableNodeIntoRect();
   void OnUpdateTopControlsState(bool enable_hiding,
                                 bool enable_showing,
@@ skipping 281 matching lines @@
   // use the Observer interface to filter IPC messages and receive frame change
   // notifications.
   // ---------------------------------------------------------------------------
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_VIEW_IMPL_H_