Revert of Make profiling lock global rather than per Target

Source/devtools/front_end/common/Lock.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.Object}
- */
-WebInspector.Lock = function()
-{
-    this._count = 0; // Reentrant.
-}
-
-/**
- * @enum {string}
- */
-WebInspector.Lock.Events = {
-    StateChanged: "StateChanged"
-}
-
-WebInspector.Lock.prototype = {
-    /**
-     * @return {boolean}
-     */
-    isAcquired: function()
-    {
-        return !!this._count;
-    },
-
-    acquire: function()
-    {
-        if (++this._count === 1)
-            this.dispatchEventToListeners(WebInspector.Lock.Events.StateChanged);
-    },
-
-    release: function()
-    {
-        --this._count;
-        if (this._count < 0) {
-            console.error("WebInspector.Lock acquire/release calls are unbalanced " + new Error().stack);
-            return;
-        }
-        if (!this._count)
-            this.dispatchEventToListeners(WebInspector.Lock.Events.StateChanged);
-    },
-
-    __proto__: WebInspector.Object.prototype
-}
-
-/** @type {!WebInspector.Lock} */
-WebInspector.profilingLock = new WebInspector.Lock();