dgeni(api-builder): hide private classes with extra underscores

Author: naomiblack

tools/api-builder/angular.io-package/index.js

@@ -48,11 +48,18 @@ module.exports = new Package('angular.io', [basePackage, targetPackage, cheatshe
   readTypeScriptModules.ignoreExportsMatching = [
     '__esModule',
     '__core_private__',
+    '___core_private__',
     '__core_private_testing__',
+    '___core_private_testing__',
+    '___core_private_testing_placeholder__',
     '__platform_browser_private__',
+    '___platform_browser_private__',
     '__platform_browser_dynamic_private__',
+    '___platform_browser_dynamic_private__',
+    '___platform_server_private__',
     '__platform_server_private__',
     '__router_private__',
+    '___router_private__',
   ];
 
   readTypeScriptModules.sourceFiles = [