Move gtest_prod_util.h out of webrtc/test tree.

webrtc/base/base.gyp

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 {
   'includes': [ '../build/common.gypi', ],
@@ skipping 728 matching lines @@
           'dependencies': [
             '<(DEPTH)/third_party/boringssl/boringssl.gyp:boringssl',
           ],
         }, {
           'include_dirs': [
             '<(ssl_root)',
           ],
         }],
       ],
     },
+    {
+     'target_name': 'gtest_prod',
+      'type': 'static_library',
+      'sources': [
+        'gtest_prod_util.h',
+      ],
+    },
   ],
 }