Remove previous Safari overhead; cleanup workarounds from rest of code

platform/firefox/vapi-client.js

@@ -166,12 +166,6 @@ window.addEventListener('pageshow', vAPI.messaging.toggleListener, true);
 
 /******************************************************************************/
 
-vAPI.canExecuteContentScript = function() {
-    return true;
-};
-
-/******************************************************************************/
-
 })(this);
 
 /******************************************************************************/