Add getYUV8Planes() API to SkCodec

src/codec/SkCodecImageGenerator.h

Index: src/codec/SkCodecImageGenerator.h
diff --git a/src/codec/SkCodecImageGenerator.h b/src/codec/SkCodecImageGenerator.h
index 80eacb19c885544c5e93bdec605e5725d91b5da5..e9dae2b485c15a28a95430c86bc18dbd73f53d0c 100644
--- a/src/codec/SkCodecImageGenerator.h
+++ b/src/codec/SkCodecImageGenerator.h
@@ -39,5 +39,9 @@ private:
     SkAutoTDelete<SkCodec> fCodec;
     SkAutoTUnref<SkData> fData;
 
+    int fYWidth;

[scroggo, 2016/01/19 18:37:48]

I think we should initialize these to some bad value (e.g. 0?) and assert that
they are not 0 when we actually need to use them.

Also, it looks like these aren't needed once we change the API of
SkImageGenerator? Can you add a comment and/or macro to only include them until
we make the change?

[msarett, 2016/01/19 22:35:27]

Done.

+    int fUWidth;
+    int fVWidth;
+
     typedef SkImageGenerator INHERITED;
 };