Bug 1524065 - part3 : remove unused message. r=baku

`resumeMedia` is used for resuming delayed autoplay, which have been replaced by notifying via the browsing context.

Differential Revision: https://phabricator.services.mozilla.com/D18139

--HG--
extra : moz-landing-system : lando

toolkit/actors/AudioPlaybackChild.jsm

@@ -34,14 +34,6 @@ class AudioPlaybackChild extends ActorChild {
       case "mediaControlStopped":
         utils.mediaSuspend = suspendTypes.SUSPENDED_STOP_DISPOSABLE;
         break;
-      case "resumeMedia":
-        // User has clicked the tab audio indicator to play a delayed
-        // media. That's clear user intent to play, so gesture activate
-        // the content document tree so that the block-autoplay logic
-        // allows the media to autoplay.
-        this.content.document.notifyUserGestureActivation();
-        utils.mediaSuspend = suspendTypes.NONE_SUSPENDED;
-        break;
       default:
         dump("Error : wrong media control msg!\n");
         break;