[iOS] Update today_extension link flags.

test/ios/gyptest-extension.py

 #!/usr/bin/env python
 
 # Copyright (c) 2014 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Verifies that ios app extensions are built correctly.
 """
 
 import TestGyp
 import TestMac
 import subprocess
+import sys
 
-def CheckStrip(p, n_expected):
-  if "ActionViewController" not in subprocess.check_output(['nm','-gU', p]):
-    print "ActionViewController shouldn't get stripped out."
+def CheckStrip(p, expected):
+  if expected not in subprocess.check_output(['nm','-gU', p]):
+    print expected + " shouldn't get stripped out."
     test.fail_test()
 
-import sys
+def CheckEntrypoint(p, expected):
+  if expected not in subprocess.check_output(['nm', p]):
+    print expected + "not found."
+    test.fail_test()
+
 if sys.platform == 'darwin' and TestMac.Xcode.Version()>="0600":
 
   test = TestGyp.TestGyp(formats=['ninja', 'xcode'])
 
   test.run_gyp('extension.gyp', chdir='extension')
 
   test.build('extension.gyp', 'ExtensionContainer', chdir='extension')
 
   # Test that the extension is .appex
   test.built_file_must_exist(
       'ExtensionContainer.app/PlugIns/ActionExtension.appex',
       chdir='extension')
 
   path = test.built_file_path(
       'ExtensionContainer.app/PlugIns/ActionExtension.appex/ActionExtension',
       chdir='extension')
   CheckStrip(path, "ActionViewController")
+  CheckEntrypoint(path, "_NSExtensionMain")
 
   test.pass_test()