Add copyright headers to remaining gyp files.

gyp/most.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.
 # Build ALMOST everything provided by Skia; this should be the default target.
 #
 # This omits the following targets that many developers won't want to build:
 # - debugger: this requires QT to build
 #
 {
   'variables': {
     'skia_skip_gui%': 0,
   },
   'targets': [
@@ skipping 37 matching lines @@
             'dependencies!': [
               'example.gyp:HelloWorld',
               'SampleApp.gyp:SampleApp',
             ]
           }
         ]
       ],
     },
   ],
 }