[WebMIDI] Fix a WebMIDIPermissionRequest leak.

content/renderer/media/midi_dispatcher.h

 // Copyright 2013 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 CONTENT_RENDERER_MEDIA_MIDI_DISPATCHER_H_
 #define CONTENT_RENDERER_MEDIA_MIDI_DISPATCHER_H_
 
 #include "base/id_map.h"
 #include "content/public/renderer/render_view_observer.h"
 #include "third_party/WebKit/public/web/WebMIDIClient.h"
@@ skipping 26 matching lines @@
       const blink::WebMIDIPermissionRequest& request);
   virtual void cancelSysexPermissionRequest(
       const blink::WebMIDIPermissionRequest& request);
 
   // Permission for using system exclusive messages has been set.
   void OnSysExPermissionApproved(int client_id, bool is_allowed);
 
   // Each WebMIDIPermissionRequest object is valid until
   // cancelSysexPermissionRequest() is called with the object, or used to call
   // WebMIDIPermissionRequest::setIsAllowed().
-  IDMap<blink::WebMIDIPermissionRequest> requests_;
+  typedef IDMap<blink::WebMIDIPermissionRequest, IDMapOwnPointer> Requests;
+  Requests requests_;
 
   DISALLOW_COPY_AND_ASSIGN(MidiDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MIDI_DISPATCHER_H_