Creating a new wrapper for gif decoder

gyp/codec.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 for codec project.
 {
   'targets': [
     {
       'target_name': 'codec',
       'product_name': 'skia_codec',
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [
         'core.gyp:*',
         'libpng.gyp:libpng',
       ],
       'include_dirs': [
         '../include/codec',
         '../src/codec',
         '../src/core',
       ],
       'sources': [
         '../src/codec/SkCodec.cpp',
         '../src/codec/SkCodec_libbmp.cpp',
+        '../src/codec/SkCodec_libgif.cpp',
         '../src/codec/SkCodec_libico.cpp',
         '../src/codec/SkCodec_libpng.cpp',
+        '../src/codec/SkGifInterlaceIter.cpp',
         '../src/codec/SkMaskSwizzler.cpp',
         '../src/codec/SkMasks.cpp',
         '../src/codec/SkSwizzler.cpp',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../include/codec',
         ],
       },
     },
   ],
 }