Add copyright headers to remaining gyp files.

gyp/pdfviewer_lib.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
 #
 {
   'targets': [
     {
       'target_name': 'pdfviewer_lib',
       'type': 'static_library',
@@ skipping 32 matching lines @@
         '../experimental/PdfViewer/pdfparser/native/pdfapi',
         '../src/core',
       ],
       'dependencies': [
         'skia_lib.gyp:skia_lib',
         'skflate.gyp:skflate',
       ],
     },
   ],
 }