DevTools: introduce TargetBreakpoints as a presentation of breakpoint and its state within target

Source/devtools/front_end/sdk/Target.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 {Protocol.Agents}
  * @param {!InspectorBackendClass.Connection} connection
@@ skipping 211 matching lines @@
     this._observers = [];
 }
 
 WebInspector.TargetManager.prototype = {
 
     /**
      * @param {!WebInspector.TargetManager.Observer} targetObserver
      */
     observeTargets: function(targetObserver)
     {
-        WebInspector.targetManager.targets().forEach(targetObserver.targetAdded.bind(targetObserver));
+        this.targets().forEach(targetObserver.targetAdded.bind(targetObserver));
         this._observers.push(targetObserver);
     },
 
     /**
+     * @param {!WebInspector.TargetManager.Observer} targetObserver
+     */
+    removeTargetObserver: function(targetObserver)
+    {
+        this._observers.remove(targetObserver);
+    },
+
+    /**
      * @param {!InspectorBackendClass.Connection} connection
      * @param {function(!WebInspector.Target)=} callback
      */
     createTarget: function(connection, callback)
     {
         var target = new WebInspector.Target(connection, callbackWrapper.bind(this));
 
         /**
          * @this {WebInspector.TargetManager}
          * @param newTarget
@@ skipping 43 matching lines @@
     /**
      * @param {!WebInspector.Target} target
      */
     targetRemoved: function(target) { },
 }
 
 /**
  * @type {!WebInspector.TargetManager}
  */
 WebInspector.targetManager;