MediaStreamCaptureIndicator: fix crash due to destruction on wrong thread

chrome/browser/media/media_stream_capture_indicator.h

 // 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.
 
 #ifndef CHROME_BROWSER_MEDIA_MEDIA_STREAM_CAPTURE_INDICATOR_H_
 #define CHROME_BROWSER_MEDIA_MEDIA_STREAM_CAPTURE_INDICATOR_H_
 
 #include <string>
 #include <vector>
 
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "chrome/browser/extensions/image_loading_tracker.h"
 #include "content/public/common/media_stream_request.h"
 #include "ui/base/models/simple_menu_model.h"
 #include "ui/gfx/image/image_skia.h"
 
 class StatusIcon;
 class StatusTray;
 
 // This indicator is owned by MediaInternals and deleted when MediaInternals
 // is deleted.
@@ skipping 98 matching lines @@
 
   // Updates the status tray menu with the new device list. This call will be
   // triggered by both AddCaptureDeviceTab() and RemoveCaptureDeviceTab().
   void UpdateStatusTrayIconContextMenu();
 
   // Updates the status tray tooltip and image according to which kind of
   // devices are being used. This function is called by
   // UpdateStatusTrayIconContextMenu().
   void UpdateStatusTrayIconDisplay(bool audio, bool video);
 
+  // Initializes image loading state.
+  void EnsureImageLoadingTracker();
+
   // Reference to our status icon - owned by the StatusTray. If null,
   // the platform doesn't support status icons.
   StatusIcon* status_icon_;
 
   // These images are owned by ResourceBundle and need not be destroyed.
   gfx::ImageSkia* mic_image_;
   gfx::ImageSkia* camera_image_;
   gfx::ImageSkia* balloon_image_;
 
   // A list that contains the usage information of the opened capture devices.
   typedef std::vector<CaptureDeviceTab> CaptureDeviceTabs;
   CaptureDeviceTabs tabs_;
 
   // Tracks the load of extension icons.
-  ImageLoadingTracker tracker_;
+  scoped_ptr<ImageLoadingTracker> tracker_;
   // The messages to display when extension images are loaded. The index
   // corresponds to the index of the associated LoadImage request.
   std::map<int, string16> pending_messages_;
   // Tracks the number of requests to |tracker_|.
   int request_index_;
 };
 
 #endif  // CHROME_BROWSER_MEDIA_MEDIA_STREAM_CAPTURE_INDICATOR_H_