Revert 235139 "Fix cancelling of device enumeration requests."

> Fix cancelling of device enumeration requests.
> 
> TEST= Log using --vmodule=media_stream_manager*=3,media_stream_dispatcher*=3 and make sure the log print out media_stream_manager.cc(316)]CancelRequest(
> after
> MediaStreamDispatcher::StopEnumerateDevices() while using the webcam on youtube.com/my_webcam?privacy=public
> 
> BUG=317534
> R=xians@chromium.org
> 
> Review URL: https://codereview.chromium.org/72683002

TBR=perkj@chromium.org

Review URL: https://codereview.chromium.org/74753005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235678 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/media/media_stream_dispatcher_host.cc

@@ -95,8 +95,6 @@ bool MediaStreamDispatcherHost::OnMessageReceived(
                         OnStopStreamDevice)
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_EnumerateDevices,
                         OnEnumerateDevices)
-    IPC_MESSAGE_HANDLER(MediaStreamHostMsg_CancelEnumerateDevices,
-                        OnCancelEnumerateDevices);
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_OpenDevice,
                         OnOpenDevice)
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_CloseDevice,