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

ui/wm/core/transient_window_manager.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/wm/core/transient_window_manager.h"
 
 #include <algorithm>
 #include <functional>
 
 #include "base/auto_reset.h"
@@ skipping 138 matching lines @@
     show_on_parent_visible_ = window_->TargetVisibility();
     window_->Hide();
   } else {
     if (show_on_parent_visible_ && parent_controls_visibility_)
       window_->Show();
     show_on_parent_visible_ = false;
   }
 }
 
 void TransientWindowManager::OnWindowVisibilityChanged(Window* window,
-                                                       bool visible) {
+    bool visible,  bool content_visible) {
   if (window_ != window)
     return;
 
   // If the window has transient children, updates the transient children's
   // visiblity as well.
   for (Window* child : transient_children_)
     Get(child)->UpdateTransientChildVisibility(visible);
 
   // Remember the show request in |show_on_parent_visible_| and hide it again
   // if the following conditions are met
@@ skipping 43 matching lines @@
 
   // Destroy transient children, only after we've removed ourselves from our
   // parent, as destroying an active transient child may otherwise attempt to
   // refocus us.
   Windows transient_children(transient_children_);
   STLDeleteElements(&transient_children);
   DCHECK(transient_children_.empty());
 }
 
 }  // namespace wm