Add copyright headers to remaining gyp files.

gyp/experimental.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 experimental directory.
 {
   'targets': [
     {
       'target_name': 'experimental',
       'type': 'static_library',
       'include_dirs': [
         '../include/config',
         '../include/core',
       ],
@@ skipping 34 matching lines @@
         '../tools/flags',
       ],
       'dependencies': [
         'pdf.gyp:pdf',
         'skia_lib.gyp:skia_lib',
         'tools.gyp:sk_tool_utils',
       ],
     },
   ],
 }