Add SkCodec, including PNG implementation.

gyp/codec.gyp

Index: gyp/codec.gyp
diff --git a/gyp/codec.gyp b/gyp/codec.gyp
new file mode 100644
index 0000000000000000000000000000000000000000..b9627995ef27a163f916ee25f93d5b984acde6ae
--- /dev/null
+++ b/gyp/codec.gyp
@@ -0,0 +1,29 @@
+# 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',
+      ],
+      'sources': [
+        '../src/codec/SkCodec.cpp',
+        '../src/codec/SkCodec_libpng.cpp',
+        '../src/codec/SkSwizzler.cpp',
+      ],
+      'direct_dependent_settings': {
+        'include_dirs': [
+          '../include/codec',
+        ],
+      },
+    },
+  ],
+}