Bug 895104 - Remove call to no-longer-existant DOMRequestIpcHelper.observe in SystemMessageManager.observe. r=fabrice

DOMRequestIpcHelper.observe was removed in bug 889984.

dom/messages/SystemMessageManager.js

@@ -282,8 +282,6 @@ SystemMessageManager.prototype = {
     if (aTopic === kSystemMessageInternalReady) {
       this._registerManifest();
     }
-    // Call the DOMRequestIpcHelper.observe method.
-    this.__proto__.__proto__.observe.call(this, aSubject, aTopic, aData);
   },
 
   _registerManifest: function sysMessMgr_registerManifest() {