Add copyright headers to remaining gyp files.

gyp/example.gyp

+# Copyright 2015 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
 # GYP file to build hello world example.
 {
   'targets': [
     {
       'target_name': 'HelloWorld',
       'type': 'executable',
       'mac_bundle' : 1,
       'include_dirs' : [
         '../include/gpu',
       ],
@@ skipping 31 matching lines @@
             'INFOPLIST_FILE' : '../example/mac/HelloWorld-Info.plist',
           },
           'mac_bundle_resources' : [
             '../example/mac/HelloWorld.xib'
           ],
         }],
       ],
     },
   ],
 }