DevTools: simplify setScriptSource and restartFrame return values

Source/core/inspector/InjectedScriptSource.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 941 matching lines @@
     /**
      * @param {!JavaScriptCallFrame} topCallFrame
      * @param {string} callFrameId
      * @return {*}
      */
     restartFrame: function(topCallFrame, callFrameId)
     {
         var callFrame = this._callFrameForId(topCallFrame, callFrameId);
         if (!callFrame)
             return "Could not find call frame with given id";
-        var result = callFrame.restart();
-        if (result === false)
-            result = "Restart frame is not supported";
-        return result;
+        return callFrame.restart();
     },
 
     /**
      * @param {!JavaScriptCallFrame} topCallFrame
      * @param {string} callFrameId
      * @return {*} a stepIn position array ready for protocol JSON or a string error
      */
     getStepInPositions: function(topCallFrame, callFrameId)
     {
         var callFrame = this._callFrameForId(topCallFrame, callFrameId);
@@ skipping 974 matching lines @@
      */
     _logEvent: function(event)
     {
         inspectedGlobalObject.console.log(event.type, event);
     }
 }
 
 injectedScript._commandLineAPIImpl = new CommandLineAPIImpl();
 return injectedScript;
 })