Fix the bug of multiple overlays.

ash/wm/partial_screenshot_view.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/partial_screenshot_view.h"
 
 #include <algorithm>
 
 #include "ash/display/mouse_cursor_event_filter.h"
 #include "ash/screenshot_delegate.h"
@@ skipping 52 matching lines @@
   // Overridden from views::WidgetObserver:
   virtual void OnWidgetDestroying(views::Widget* widget) OVERRIDE {
     widget->RemoveObserver(this);
     widgets_.erase(std::remove(widgets_.begin(), widgets_.end(), widget));
     if (widgets_.empty())
       delete this;
   }
 
  private:
   virtual ~OverlayDelegate() {
-    Shell::GetInstance()->overlay_filter()->Deactivate();
+    Shell::GetInstance()->overlay_filter()->Deactivate(this);
   }
 
   std::vector<views::Widget*> widgets_;
 
   DISALLOW_COPY_AND_ASSIGN(OverlayDelegate);
 };
 
 // static
 std::vector<PartialScreenshotView*>
 PartialScreenshotView::StartPartialScreenshot(
     ScreenshotDelegate* screenshot_delegate) {
   std::vector<PartialScreenshotView*> views;
+
+  if (Shell::GetInstance()->overlay_filter()->IsActive())
+    return views;
+
   OverlayDelegate* overlay_delegate = new OverlayDelegate();
   aura::Window::Windows root_windows = Shell::GetAllRootWindows();
   for (aura::Window::Windows::iterator it = root_windows.begin();
        it != root_windows.end(); ++it) {
     PartialScreenshotView* new_view = new PartialScreenshotView(
         overlay_delegate, screenshot_delegate);
     new_view->Init(*it);
     views.push_back(new_view);
   }
   return views;
@@ skipping 136 matching lines @@
       OnSelectionFinished();
       break;
     default:
       break;
   }
 
   event->SetHandled();
 }
 
 }  // namespace ash