[WebMIDI] Fix a WebMIDIPermissionRequest leak.

IDMap<T, OS> owns its values only if OS == IDMapOwnPtr.

BUG=NONE
R=toyoshim@chromium.org

Review URL: https://codereview.chromium.org/323083002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@276614 0039d316-1c4b-4281-b951-d872f2087c98

content/renderer/media/midi_dispatcher.cc

@@ -44,9 +44,7 @@ void MidiDispatcher::requestSysexPermission(
 
 void MidiDispatcher::cancelSysexPermissionRequest(
     const WebMIDIPermissionRequest& request) {
-  for (IDMap<WebMIDIPermissionRequest>::iterator it(&requests_);
-       !it.IsAtEnd();
-       it.Advance()) {
+  for (Requests::iterator it(&requests_); !it.IsAtEnd(); it.Advance()) {
     WebMIDIPermissionRequest* value = it.GetCurrentValue();
     if (value->equals(request)) {
       base::string16 origin = request.securityOrigin().toString();

content/renderer/media/midi_dispatcher.h

@@ -44,7 +44,8 @@ class MidiDispatcher : public RenderViewObserver,
   // 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);
 };