fix: don’t use the global `ng` at all with closure enhanced optimizations

This is needed as:
- closure declares globals itself for minified names, which sometimes clobber our `ng` global
- we can't declare a closure extern as the namespace `ng` is already used within Google for typings for angularJS (via `goog.provide('ng....')`).

packages/core/src/core.externs.js

@@ -8,10 +8,10 @@
  * @externs
  */
 
-/**
- * @suppress {duplicate}
- */
-var ng;
+// Note: we can't declare an extern for the global variable `ng` as
+// the namespace `ng` is already used within Google
+// for typings for angularJS (via `goog.provide('ng....')`).
+
 /**
  * @suppress {duplicate}
  */

packages/goog.d.ts

@@ -0,0 +1,15 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+
+/**
+ * Typings for google closure.
+ */
+declare namespace goog {
+  export const DEBUG: boolean;
+}

packages/platform-browser/src/dom/util.ts

@@ -28,10 +28,12 @@ export function dashCaseToCamelCase(input: string): string {
  * @param value The value to export.
  */
 export function exportNgVar(name: string, value: any): void {
-  if (!ng) {
-    global['ng'] = ng = (global['ng'] as{[key: string]: any} | undefined) || {};
+  if (typeof goog === 'undefined' || goog.DEBUG) {
+    // Note: we can't export `ng` when using closure enhanced optimization as:
+    // - closure declares globals itself for minified names, which sometimes clobber our `ng` global
+    // - we can't declare a closure extern as the namespace `ng` is already used within Google
+    //   for typings for angularJS (via `goog.provide('ng....')`).
+    const ng = global['ng'] = (global['ng'] as{[key: string]: any} | undefined) || {};
+    ng[name] = value;
   }
-  ng[name] = value;
 }
-
-let ng: {[key: string]: any}|undefined;

packages/platform-browser/tsconfig-build.json

@@ -15,7 +15,8 @@
   "files": [
     "public_api.ts",
     "../../node_modules/@types/hammerjs/index.d.ts",
-    "../../node_modules/zone.js/dist/zone.js.d.ts"
+    "../../node_modules/zone.js/dist/zone.js.d.ts",
+    "../goog.d.ts"
   ],
 
   "angularCompilerOptions": {

packages/types.d.ts

@@ -15,3 +15,4 @@
 /// <reference path="../node_modules/@types/selenium-webdriver/index.d.ts" />
 /// <reference path="./es6-subset.d.ts" />
 /// <reference path="./system.d.ts" />
+/// <reference path="./goog.d.ts" />