Add copyright headers to remaining gyp files.

gyp/flags.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 flag parser
 #
 {
   'targets': [
     {
       'target_name': 'flags',
       'type': 'static_library',
       'include_dirs': [ '../src/core', ],
       'sources': [
         '../tools/flags/SkCommandLineFlags.cpp',
@@ skipping 20 matching lines @@
         'flags.gyp:flags',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../tools/flags',
         ],
       }
     },
   ],
 }