Add copyright headers to remaining gyp files.

gyp/bench.gypi

+# Copyright 2015 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
 {
   'include_dirs': [
     '../src/core',
     '../src/effects',
     '../src/gpu',
     '../src/utils',
     '../tools',
   ],
   'dependencies': [
     'etc1.gyp:libetc1',
@@ skipping 90 matching lines @@
     '../bench/StrokeBench.cpp',
     '../bench/TableBench.cpp',
     '../bench/TextBench.cpp',
     '../bench/TileBench.cpp',
     '../bench/VertBench.cpp',
     '../bench/WritePixelsBench.cpp',
     '../bench/WriterBench.cpp',
     '../bench/XfermodeBench.cpp',
   ],
 }