[DevTools] Support all targets discovery in Target domain.

third_party/WebKit/Source/devtools/front_end/sdk/SubTargetsManager.js

 // Copyright 2016 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.SDKModel}
  * @param {!WebInspector.Target} target
  */
 WebInspector.SubTargetsManager = function(target)
 {
     WebInspector.SDKModel.call(this, WebInspector.SubTargetsManager, target);
     target.registerTargetDispatcher(new WebInspector.SubTargetsDispatcher(this));
     this._lastAnonymousTargetId = 0;
     this._agent = target.targetAgent();
 
     /** @type {!Map<string, !WebInspector.TargetInfo>} */
     this._allTargets = new Map();
 
     /** @type {!Map<string, !WebInspector.Target>} */
     this._attachedTargets = new Map();
     /** @type {!Map<string, !WebInspector.SubTargetConnection>} */
     this._connections = new Map();
 
     this._agent.setAutoAttach(true /* autoAttach */, true /* waitForDebuggerOnStart */);
     this._agent.setAttachToFrames(Runtime.experiments.isEnabled("autoAttachToCrossProcessSubframes"));
-    this._agent.enable();
 }
 
 /** @enum {symbol} */
 WebInspector.SubTargetsManager.Events = {
     SubTargetAdded: Symbol("SubTargetAdded"),
     SubTargetRemoved: Symbol("SubTargetRemoved"),
 }
 
 WebInspector.SubTargetsManager._InfoSymbol = Symbol("SubTargetInfo");
 
@@ skipping 278 matching lines @@
     this.url = payload.url;
     this.type = payload.type;
     if (this.type !== "page" && this.type !== "iframe") {
         this.title = WebInspector.UIString("Worker: %s", this.url);
         this.canActivate = false;
     } else {
         this.title = payload.title;
         this.canActivate = true;
     }
 }