DevTools: improve identifier extraction in SourceMapNamesResolver

third_party/WebKit/Source/devtools/front_end/es_tree/ESTreeWalker.js

 // Copyright (c) 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
  * @param {function(!ESTree.Node)} beforeVisit
- * @param {function(!ESTree.Node)} afterVisit
+ * @param {function(!ESTree.Node)=} afterVisit
  */
 WebInspector.ESTreeWalker = function(beforeVisit, afterVisit)
 {
     this._beforeVisit = beforeVisit;
-    this._afterVisit = afterVisit;
+    this._afterVisit = afterVisit || new Function();
 }
 
+WebInspector.ESTreeWalker.SkipSubtree = {};
+
 WebInspector.ESTreeWalker.prototype = {
     /**
      * @param {!ESTree.Node} ast
      */
     walk: function(ast)
     {
         this._innerWalk(ast, null);
     },
 
     /**
      * @param {!ESTree.Node} node
      * @param {?ESTree.Node} parent
      */
     _innerWalk: function(node, parent)
     {
         if (!node)
             return;
         node.parent = parent;
 
-        this._beforeVisit.call(null, node);
+        if (this._beforeVisit.call(null, node) === WebInspector.ESTreeWalker.SkipSubtree) {
+            this._afterVisit.call(null, node);
+            return;
+        }
 
         var walkOrder = WebInspector.ESTreeWalker._walkOrder[node.type];
         if (!walkOrder) {
             console.error("Walk order not defined for " + node.type);
             return;
         }
 
         if (node.type === "TemplateLiteral") {
             var templateLiteral = /** @type {!ESTree.TemplateLiteralNode} */ (node);
             var expressionsLength = templateLiteral.expressions.length;
@@ skipping 72 matching lines @@
     "ThrowStatement": ["argument"],
     "TryStatement": ["block", "handler", "finalizer"],
     "UnaryExpression": ["argument"],
     "UpdateExpression": ["argument"],
     "VariableDeclaration": ["declarations"],
     "VariableDeclarator": ["id", "init"],
     "WhileStatement": ["test", "body"],
     "WithStatement": ["object", "body"],
     "YieldExpression": ["argument"]
 }