Fix in compiler pass: cr.define() can export variable without assigned value

third_party/closure_compiler/runner/src/com/google/javascript/jscomp/ChromePass.java

 // 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.
 
 package com.google.javascript.jscomp;
 
 import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
 import com.google.javascript.rhino.IR;
 import com.google.javascript.rhino.JSDocInfoBuilder;
 import com.google.javascript.rhino.JSTypeExpression;
@@ skipping 277 matching lines @@
 
                 if (n.getJSDocInfo() != null) {
                     exprResult.getFirstChild().setJSDocInfo(n.getJSDocInfo());
                     functionTree.removeProp(Node.JSDOC_INFO_PROP);
                 }
                 this.namespaceBlock.replaceChild(n, exprResult);
             } else if (n.isName() && this.exports.containsKey(n.getString()) &&
                     !parent.isFunction()) {
                 if (parent.isVar()) {
                     if (parent.getParent() == this.namespaceBlock) {
-                        // It's a top-level exported variable definition.
+                        // It's a top-level exported variable definition (maybe without an
+                        // assignment).
                         // Change
                         //
                         //   var enum = { 'one': 1, 'two': 2 };
                         //
                         // to
                         //
                         //   my.namespace.name.enum = { 'one': 1, 'two': 2 };
                         Node varContent = n.removeFirstChild();
-                        Node exprResult = IR.exprResult(
-                                    IR.assign(buildQualifiedName(n), varContent).srcref(parent)
-                                ).srcref(parent);
-
+                        Node exprResult;
+                        if (varContent == null) {
+                            exprResult = IR.exprResult(buildQualifiedName(n)).srcref(parent);
+                        } else {
+                            exprResult = IR.exprResult(
+                                        IR.assign(buildQualifiedName(n), varContent).srcref(parent)
+                                    ).srcref(parent);
+                        }
                         if (parent.getJSDocInfo() != null) {
                             exprResult.getFirstChild().setJSDocInfo(parent.getJSDocInfo().clone());
                         }
                         this.namespaceBlock.replaceChild(parent, exprResult);
                     }
                 } else {
                     // It's a local name referencing exported entity. Change to its global name.
                     Node newNode = buildQualifiedName(n);
                     if (n.getJSDocInfo() != null) {
                         newNode.setJSDocInfo(n.getJSDocInfo().clone());
@@ skipping 11 matching lines @@
         }
 
         private Node buildQualifiedName(Node internalName) {
             String externalName = this.exports.get(internalName.getString());
             return NodeUtil.newQualifiedNameNode(compiler.getCodingConvention(),
                     this.namespaceName + "." + externalName).srcrefTree(internalName);
         }
     }
 
 }