Move the injection test API to content/public.

chrome/test/security_tests/security_tests.gyp

 # Copyright (c) 2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
       'target_name': 'security_tests',
       'type': 'shared_library',
       'sources': [
         '../../../sandbox/win/tests/validation_tests/commands.cc',
         '../../../sandbox/win/tests/validation_tests/commands.h',
-        '../injection_test_dll.h',
         'ipc_security_tests.cc',
         'ipc_security_tests.h',
         'security_tests.cc',
       ],
     },
   ],
 }