RootWindowController::GetFullscreenWindow() should return the active one.

ash/wm/gestures/shelf_gesture_handler.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 "ash/wm/gestures/shelf_gesture_handler.h"
 
 #include "ash/root_window_controller.h"
 #include "ash/session_state_delegate.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shelf/shelf_types.h"
@@ skipping 27 matching lines @@
     return false;
   }
 
   // TODO(oshima): Find the root window controller from event's location.
   RootWindowController* controller = Shell::GetPrimaryRootWindowController();
 
   ShelfLayoutManager* shelf = controller->GetShelfLayoutManager();
 
   // The gesture are disabled for fullscreen windows that are not in immersive
   // mode.
-  const aura::Window* fullscreen = controller->GetFullscreenWindow();
+  const aura::Window* fullscreen = controller->GetTopmostFullscreenWindow();
   if (fullscreen && !shelf->FullscreenWithMinimalChrome())
     return false;
 
   if (event.type() == ui::ET_GESTURE_SCROLL_BEGIN) {
     drag_in_progress_ = true;
     shelf->StartGestureDrag(event);
     return true;
   }
 
   if (!drag_in_progress_)
@@ skipping 24 matching lines @@
     return true;
   }
 
   // Unexpected event. Reset the state and let the event fall through.
   shelf->CancelGestureDrag();
   return false;
 }
 
 }  // namespace internal
 }  // namespace ash