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

ui/wm/core/window_modality_controller.cc

 // 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.
 
 #include "ui/wm/core/window_modality_controller.h"
 
 #include <algorithm>
 
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/capture_client.h"
@@ skipping 141 matching lines @@
       window->GetProperty(aura::client::kModalKey) != ui::MODAL_TYPE_NONE &&
       window->IsVisible()) {
     ActivateWindow(window);
     ui::GestureRecognizer::Get()->TransferEventsTo(GetTransientParent(window),
                                                    NULL);
   }
 }
 
 void WindowModalityController::OnWindowVisibilityChanged(
     aura::Window* window,
-    bool visible) {
+    bool visible, bool content_visible) {
   if (visible && window->GetProperty(aura::client::kModalKey) !=
       ui::MODAL_TYPE_NONE) {
     ui::GestureRecognizer::Get()->TransferEventsTo(GetTransientParent(window),
                                                    NULL);
     // Make sure no other window has capture, otherwise |window| won't get mouse
     // events.
     aura::Window* capture_window = aura::client::GetCaptureWindow(window);
     if (capture_window)
       capture_window->ReleaseCapture();
   }
@@ skipping 19 matching lines @@
     }
 
     AnimateWindow(modal_transient_child, WINDOW_ANIMATION_TYPE_BOUNCE);
   }
   if (event->type() == ui::ET_TOUCH_CANCELLED)
     return false;
   return !!modal_transient_child;
 }
 
 }  // namespace wm