[DevTools] Roll closure compiler to ToT version

third_party/WebKit/Source/devtools/front_end/timeline/TimelineProfileTree.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.
 
 WebInspector.TimelineProfileTree = { };
 
 /**
  * @constructor
  */
 WebInspector.TimelineProfileTree.Node = function()
@@ skipping 154 matching lines @@
             }
             tdNode = tdNode.parent;
             buParent = buNode;
         }
     }
 
     // Purge zero self time nodes.
     var rootChildren = buRoot.children;
     for (var item of rootChildren.entries()) {
         if (item[1].selfTime === 0)
-            rootChildren.delete(item[0]);
+            rootChildren.delete(/** @type {string} */(item[0]));
     }
 
     return buRoot;
 
 }