Revert of Make profiling lock global rather than per Target

Source/devtools/front_end/sdk/TracingModel.js

 /*
  * Copyright 2014 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /**
  * @constructor
  * @extends {WebInspector.SDKObject}
  */
@@ skipping 83 matching lines @@
         return this._devtoolsWorkerMetadataEvents;
     },
 
     /**
      * @param {string} categoryFilter
      * @param {string} options
      * @param {function(?string)=} callback
      */
     start: function(categoryFilter, options, callback)
     {
-        WebInspector.profilingLock.acquire();
+        this.target().profilingLock.acquire();
         this.reset();
         var bufferUsageReportingIntervalMs = 500;
         TracingAgent.start(categoryFilter, options, bufferUsageReportingIntervalMs, callback);
         this._active = true;
     },
 
     stop: function()
     {
         if (!this._active)
             return;
         TracingAgent.end(this._onStop.bind(this));
-        WebInspector.profilingLock.release();
+        this.target().profilingLock.release();
     },
 
     /**
      * @return {?string}
      */
     sessionId: function()
     {
         return this._sessionId;
     },
 
@@ skipping 549 matching lines @@
     started: function(consoleTimeline, sessionId)
     {
         this._tracingModel._tracingStarted(sessionId);
     },
 
     stopped: function()
     {
         this._tracingModel._onStop();
     }
 }