Revert of Change SkDecodingImageGenerator API

src/lazy/SkDiscardablePixelRef.h

Index: src/lazy/SkDiscardablePixelRef.h
diff --git a/src/lazy/SkDiscardablePixelRef.h b/src/lazy/SkDiscardablePixelRef.h
index 3367096c266793f6b38756c6c43c50f34f275c81..4b6693837d5ade9f8a91c5dfae304b94b774f7d6 100644
--- a/src/lazy/SkDiscardablePixelRef.h
+++ b/src/lazy/SkDiscardablePixelRef.h
@@ -13,15 +13,6 @@
 #include "SkImageInfo.h"
 #include "SkPixelRef.h"
 
-/**
- *  A PixelRef backed by SkDiscardableMemory, with the ability to
- *  re-generate the pixels (via a SkImageGenerator) if the DM is
- *  purged.
- *
- *  Since SkColorTable is reference-counted, we do not support indexed
- *  color with this class; there would be no way for the discardable
- *  memory system to unref the color table.
- */
 class SkDiscardablePixelRef : public SkPixelRef {
 public:
     SK_DECLARE_UNFLATTENABLE_OBJECT()