Add SkCodec, including PNG implementation.

gyp/common_variables.gypi

 # Copyright 2012 The Android Open Source Project
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   # Get ready for the ugly...
   #
   # - We have to nest our variables dictionaries multiple levels deep, so that
   #   this and other gyp files can rely on previously-set variable values in
@@ skipping 103 matching lines @@
           # skia_freetype_static - on OS variants that normally would
           #     dynamically link the system FreeType library, don't do
           #     that; instead statically link to the version in
           #     third_party/freetype and third_party/externals/freetype.
           {
             'skia_freetype_static%': '1',
           }, {
             'skia_freetype_static%': '0',
           }
         ],
+        [ 'skia_os in ["mac", "ios", "win"]', {
+            # skia_libpng_static - instead of linking libpng with '-lpng' and
+            #     including the headers from '/usr/include/png.h', compile and
+            #     statically link the version of libpng in
+            #     third_party/externals/libpng.
+            'skia_libpng_static%': '1',
+          }, {
+            'skia_libpng_static%': '0',
+          }
+        ],
       ],
 
       # skia_giflib_static - on OS variants that normally would link giflib
       #     with '-lgif' and include the headers from '/usr/include/gif_lib.h',
       #     don't do that; instead compile and staticlly link the version of
       #     giflib in third_party/externals/giflib.
       'skia_giflib_static%': '0',
 
-      # skia_libpng_static - on OS variants that normally would link libpng
-      #     with '-lpng' and include the headers from '/usr/include/png.h',
-      #     don't do that; instead compile and staticlly link the version of
-      #     libpng in third_party/externals/libpng.
-      'skia_libpng_static%': '0',
 
       # skia_no_fontconfig - On POSIX systems that would normally use the
       #     SkFontHost_fontconfig interface; use the SkFontHost_linux
       #     version instead.
       'skia_no_fontconfig%': '0',
 
       'skia_sanitizer%': '',
       'skia_scalar%': 'float',
       'skia_mesa%': 0,
       'skia_stroke_path_rendering%': 0,
@@ skipping 93 matching lines @@
     'skia_moz2d%': 0,
     'skia_is_bot%': '<!(python -c "import os; print os.environ.get(\'CHROME_HEADLESS\', 0)")',
     'skia_egl%': '<(skia_egl)',
 
     # These are referenced by our .gypi files that list files (e.g. core.gypi)
     #
     'skia_src_path%': '../src',
     'skia_include_path%': '../include',
   },
 }