Devtools: Use Event.deepPath as a function if available.

third_party/WebKit/Source/devtools/front_end/devtools.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.
 
 (function(window) {
 
 // DevToolsAPI ----------------------------------------------------------------
 
 /**
  * @constructor
@@ skipping 943 matching lines @@
 
 if (!DOMTokenList.prototype.__originalDOMTokenListToggle) {
     DOMTokenList.prototype.__originalDOMTokenListToggle = DOMTokenList.prototype.toggle;
     DOMTokenList.prototype.toggle = function(token, force)
     {
         if (arguments.length === 1)
             force = !this.contains(token);
         return this.__originalDOMTokenListToggle(token, !!force);
     }
 }
+
+// Support for legacy (<M49) frontends. Remove in M52.
+if (Object.getOwnPropertyDescriptor(Event.prototype, "deepPath"))

[dgozman, 2016/02/02 02:45:45]

Please move this code (and a block above while we are here) into
installBackwardsCompatibility method.

[samli, 2016/02/03 00:07:11]

Done.

+    Event.prototype.deepPath = undefined;