fix: create proper externs so that closure does not clobber e.g. `ng` for internal variables (#19423)

packages/core/src/core.externs.js

@@ -0,0 +1,18 @@
+/**
+ * @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
+ *
+ * @externs
+ */
+
+/**
+ * @suppress {duplicate}
+ */
+var ng;
+/**
+ * @suppress {duplicate}
+ */
+var wtf;

packages/core/src/util.ts

@@ -21,6 +21,11 @@ const __self = typeof self !== 'undefined' && typeof WorkerGlobalScope !== 'unde
     self instanceof WorkerGlobalScope && self;
 const __global = typeof global !== 'undefined' && global;
 const _global: {[name: string]: any} = __window || __global || __self;
+/**
+ * Attention: whenever providing a new value, be sure to add an
+ * entry into the corresponding `....externs.js` file,
+ * so that closure won't use that global for its purposes.
+ */
 export {_global as global};
 
 // When Symbol.iterator doesn't exist, retrieves the key used in es6-shim

packages/platform-browser/src/dom/events/dom_events.ts

@@ -6,7 +6,10 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Inject, Injectable, NgZone, ɵglobal as global} from '@angular/core';
+import {Inject, Injectable, NgZone} from '@angular/core';
+// Import zero symbols from zone.js. This causes the zone ambient type to be
+// added to the type-checker, without emitting any runtime module load statement
+import {} from 'zone.js';
 
 import {DOCUMENT} from '../dom_tokens';
 
@@ -18,8 +21,8 @@ import {EventManagerPlugin} from './event_manager';
  * efficient bookkeeping than Zone can, because we have additional information. This speeds up
  * addEventListener by 3x.
  */
-const Zone = global['Zone'];
+const __symbol__ =
-const __symbol__ = Zone && Zone['__symbol__'] || function<T>(v: T): T {
+    (typeof Zone !== 'undefined') && (Zone as any)['__symbol__'] || function<T>(v: T): T {
   return v;
 };
 const ADD_EVENT_LISTENER: 'addEventListener' = __symbol__('addEventListener');
@@ -32,7 +35,8 @@ const ANGULAR = 'ANGULAR';
 const NATIVE_ADD_LISTENER = 'addEventListener';
 const NATIVE_REMOVE_LISTENER = 'removeEventListener';
 
-const blackListedEvents: string[] = Zone && Zone[__symbol__('BLACK_LISTED_EVENTS')];
+const blackListedEvents: string[] =
+    (typeof Zone !== 'undefined') && (Zone as any)[__symbol__('BLACK_LISTED_EVENTS')];
 let blackListedMap: {[eventName: string]: string};
 if (blackListedEvents) {
   blackListedMap = {};

packages/platform-browser/src/platform-browser.externs.js

@@ -0,0 +1,26 @@
+/**
+ * @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
+ *
+ * @externs
+ */
+
+/**
+ * @suppress {duplicate}
+ */
+var getAngularTestability;
+/**
+ * @suppress {duplicate}
+ */
+var getAllAngularTestabilities;
+/**
+ * @suppress {duplicate}
+ */
+var getAllAngularRootElements;
+/**
+ * @suppress {duplicate}
+ */
+var frameworkStabilizers;