fix(bundles): testing bundle should include browser platform

Closes angular#6626

Author: alexeagle

tools/build/webpack/angular2-all-testing.umd.js

@@ -1,18 +1,24 @@
 // this bundle is almost identical to the angular2.umd.js
-// the only difference being "testing" export
+// the only difference being "testing" exports
 exports.core = require('angular2/core');
 exports.common = require('angular2/common');
 exports.compiler = require('angular2/compiler');
 exports.platform = {
   browser: require('angular2/platform/browser'),
-  common_dom: require('angular2/platform/common_dom')
+  common_dom: require('angular2/platform/common_dom'),
+
+  // this is included as compared to the angular2-all.umd.js bundle
+  testing: {
+    browser: require('angular2/platform/testing/browser')
+  }
 };
 exports.http = require('angular2/http');
 exports.router = require('angular2/router');
 exports.router_link_dsl = require('angular2/router/router_link_dsl.js');
 exports.instrumentation = require('angular2/instrumentation');
 exports.upgrade = require('angular2/upgrade');
-// this is the only difference as compared to the angular2-all.umd.js bundle
+
+// this is included as compared to the angular2-all.umd.js bundle
 exports.testing = require('angular2/testing');
 exports.http.testing = require('angular2/http/testing');
 exports.router.testing = require('angular2/router/testing');