Add copyright headers to remaining gyp files.

gyp/pdfviewer.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 pdfviewer.
 #
 # To build on Linux:
 #  ./gyp_skia pdfviewer.gyp && make pdfviewer
 #
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
@@ skipping 26 matching lines @@
         # For SkBitmapHasher.h
         '../src/utils/',
       ],
       'dependencies': [
         'flags.gyp:flags',
         'skia_lib.gyp:skia_lib',
       ],
     },
   ],
 }