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

ui/aura/window.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 UI_AURA_WINDOW_H_
 #define UI_AURA_WINDOW_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 118 matching lines @@
   void set_host(WindowTreeHost* host) { host_ = host; }
   bool IsRootWindow() const { return !!host_; }
 
   // The Window does not own this object.
   void set_user_data(void* user_data) { user_data_ = user_data; }
   void* user_data() const { return user_data_; }
 
   // Changes the visibility of the window.
   void Show();
   void Hide();
+#if defined(OS_LINUX)
+  void SetPageVisibility(bool visibility);
+#endif
   // Returns true if this window and all its ancestors are visible.
   bool IsVisible() const;
   // Returns the visibility requested by this window. IsVisible() takes into
   // account the visibility of the layer and ancestors, where as this tracks
   // whether Show() without a Hide() has been invoked.
   bool TargetVisibility() const { return visible_; }
 
   // Returns the window's bounds in root window's coordinates.
   gfx::Rect GetBoundsInRootWindow() const;
 
@@ skipping 286 matching lines @@
       const WindowObserver::HierarchyChangeParams& params);
   // Notifies this window and its parent hierarchy.
   void NotifyWindowHierarchyChangeUp(
       const WindowObserver::HierarchyChangeParams& params);
   // Notifies this window's observers.
   void NotifyWindowHierarchyChangeAtReceiver(
       const WindowObserver::HierarchyChangeParams& params);
 
   // Methods implementing visibility change notifications. See WindowObserver
   // for more details.
-  void NotifyWindowVisibilityChanged(aura::Window* target, bool visible);
+  void NotifyWindowVisibilityChanged(aura::Window* target, bool visible,
+                                     bool content_visible);
   // Notifies this window's observers. Returns false if |this| was deleted
   // during the call (by an observer), otherwise true.
   bool NotifyWindowVisibilityChangedAtReceiver(aura::Window* target,
-                                               bool visible);
+                                               bool visible,
+                                               bool content_visible);
   // Notifies this window and its child hierarchy. Returns false if
   // |this| was deleted during the call (by an observer), otherwise
   // true.
-  bool NotifyWindowVisibilityChangedDown(aura::Window* target, bool visible);
+  bool NotifyWindowVisibilityChangedDown(aura::Window* target,
+                                         bool visible,
+                                       bool content_visible);
   // Notifies this window and its parent hierarchy.
   void NotifyWindowVisibilityChangedUp(aura::Window* target, bool visible);
 
   // Notifies this window and its child hierarchy of a transform applied to
   // |source|.
   void NotifyAncestorWindowTransformed(Window* source);
 
   // Invoked when the bounds of the window changes. This may be invoked directly
   // by us, or from the closure returned by PrepareForLayerBoundsChange() after
   // the bounds of the layer has changed. |old_bounds| is the previous bounds.
@@ skipping 82 matching lines @@
   };
 
   std::map<const void*, Value> prop_map_;
 
   DISALLOW_COPY_AND_ASSIGN(Window);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_H_