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

ui/aura/window_event_dispatcher.cc

 // Copyright 2014 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.
 
 #include "ui/aura/window_event_dispatcher.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 561 matching lines @@
 
 void WindowEventDispatcher::OnWindowVisibilityChanging(Window* window,
                                                        bool visible) {
   if (!host_->window()->Contains(window))
     return;
 
   DispatchMouseExitToHidingWindow(window);
 }
 
 void WindowEventDispatcher::OnWindowVisibilityChanged(Window* window,
-                                                      bool visible) {
+                                                      bool visible,
+                                                      bool content_visible) {
   if (!host_->window()->Contains(window))
     return;
 
   if (window->ContainsPointInRoot(GetLastMouseLocationInRoot()))
     PostSynthesizeMouseMove();
 
   // Hiding the window releases capture which can implicitly destroy the window
   // so the window may no longer be valid after this call.
   if (!visible)
     OnWindowHidden(window, WINDOW_HIDDEN);
@@ skipping 298 matching lines @@
   }
 
   // This flag is set depending on the gestures recognized in the call above,
   // and needs to propagate with the forwarded event.
   event->set_may_cause_scrolling(orig_event.may_cause_scrolling());
 
   PreDispatchLocatedEvent(target, event);
 }
 
 }  // namespace aura