media: Add MediaPermission interface and MediaPermissionDispatcher.

mojo/services/html_viewer/html_document.cc

Index: mojo/services/html_viewer/html_document.cc
diff --git a/mojo/services/html_viewer/html_document.cc b/mojo/services/html_viewer/html_document.cc
index a692958165c48d5e03acfc819487a340ed8ea757..eca0d00731576f42303e205352874772c4bf13ec 100644
--- a/mojo/services/html_viewer/html_document.cc
+++ b/mojo/services/html_viewer/html_document.cc
@@ -277,8 +277,10 @@ void HTMLDocument::didNavigateWithinPage(
 
 blink::WebEncryptedMediaClient* HTMLDocument::encryptedMediaClient() {
   if (!web_encrypted_media_client_) {
+    // TODO(xhwang): Hook up permission services and add a MediaPermission
+    // implementation for HTMLDocument.
     web_encrypted_media_client_.reset(new media::WebEncryptedMediaClientImpl(
-        make_scoped_ptr(new media::DefaultCdmFactory())));
+        make_scoped_ptr(new media::DefaultCdmFactory()), nullptr));
   }
   return web_encrypted_media_client_.get();
 }