[Win, MediaGallery] Enumerate and handle mtp device attach/detach events.

chrome/browser/chrome_browser_main_win.h

Index: chrome/browser/chrome_browser_main_win.h
diff --git a/chrome/browser/chrome_browser_main_win.h b/chrome/browser/chrome_browser_main_win.h
index 4094013d77b123765addb7bf8e493d0e5a148f4c..9d1459f841e0bf4be3eb44fb65a9744f1ddc3c14 100644
--- a/chrome/browser/chrome_browser_main_win.h
+++ b/chrome/browser/chrome_browser_main_win.h
@@ -15,6 +15,11 @@ class MetroViewerProcessHost;
 
 namespace chrome {
 class RemovableDeviceNotificationsWindowWin;
+
+namespace mtp {
+class MediaTransferProtocolDeviceObserverWin;
+}  // namespace mtp
+
 }  // namespace chrome
 
 
@@ -68,6 +73,8 @@ class ChromeBrowserMainPartsWin : public ChromeBrowserMainParts {
   static void SetupInstallerUtilStrings();
 
  private:
+  scoped_refptr<chrome::mtp::MediaTransferProtocolDeviceObserverWin>
+      media_transfer_protocol_device_observer_;
   scoped_refptr<chrome::RemovableDeviceNotificationsWindowWin>
       removable_device_notifications_window_;
 #if defined(USE_AURA)