Make Page Visibility API work when the browser window is visible or not

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 <deque>
 #include <map>
 #include <set>
@@ skipping 657 matching lines @@
   void OnStopFinding(StopFindAction action);
   void OnSuppressDialogsUntilSwapOut();
   void OnThemeChanged();
   void OnUpdateTargetURLAck();
   void OnUpdateWebPreferences(const WebPreferences& prefs);
   void OnResetPageScale();
   void OnZoom(PageZoom zoom);
   void OnEnableViewSourceMode();
   void OnForceRedraw(int request_id);
   void OnSelectWordAroundCaret();
+  void OnSetWindowVisibility(bool visible);
 #if defined(OS_ANDROID)
   void OnActivateNearestFindResult(int request_id, float x, float y);
   void OnFindMatchRects(int current_version);
   void OnUndoScrollFocusedEditableNodeIntoRect();
   void OnUpdateTopControlsState(bool enable_hiding,
                                 bool enable_showing,
                                 bool animate);
   void OnExtractSmartClipData(const gfx::Rect& rect);
 #elif defined(OS_MACOSX)
   void OnGetRenderedText();
   void OnPluginImeCompositionCompleted(const base::string16& text,
                                        int plugin_id);
   void OnSetInLiveResize(bool in_live_resize);
-  void OnSetWindowVisibility(bool visible);
   void OnWindowFrameChanged(const gfx::Rect& window_frame,
                             const gfx::Rect& view_frame);
 #endif
 
   // Adding a new message handler? Please add it in alphabetical order above
   // and put it in the same position in the .cc file.
 
   // Misc private functions ----------------------------------------------------
   // Check whether the preferred size has changed.
   void CheckPreferredSize();
@@ skipping 315 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_