Add SkCodec, including PNG implementation.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index c4068dbdcf892b447bb495673941604d53cd8994..c17963894c11a72f2830eb6179b8d8d0383f3581 100644
--- a/DEPS
+++ b/DEPS
@@ -17,6 +17,7 @@ deps = {
   "third_party/externals/libjpeg" : "https://chromium.googlesource.com/chromium/deps/libjpeg_turbo.git@82ce8a6d4ebe12a177c0c3597192f2b4f09e81c3",
   "third_party/externals/libwebp" : "https://chromium.googlesource.com/webm/libwebp.git@3fe91635df8734b23f3c1b9d1f0c4fa8cfaf4e39",
   "third_party/externals/nanomsg": "https://skia.googlesource.com/third_party/nanomsg.git@0.4-beta",
+  "third_party/externals/libpng": "https://github.com/glennrp/libpng.git@c6b29ff896a013961b41375c7fdac94b20513ae0",

[djsollen, 2015/02/25 20:52:15]

why not git://git.code.sf.net/p/libpng/code libpng-code?  Can we also depend on
the tag libpng-1.6.16-signed

[scroggo, 2015/02/25 21:33:52]

Ok, I updated it to pull from SourceForge at commit
070a616b8275277e18ef8ee91e2ca23f7bdc67d5, which appears to be the commit with
that tag.

 
   "platform_tools/android/third_party/externals/expat" : "https://android.googlesource.com/platform/external/expat.git@android-4.2.2_r1.2",
   "platform_tools/android/third_party/externals/gif" : "https://android.googlesource.com/platform/external/giflib.git@android-4.2.2_r1.2",