Make BitmapRegionDecoder succeed on invalid requests

src/android/SkBitmapRegionCanvas.h

Index: src/android/SkBitmapRegionCanvas.h
diff --git a/src/android/SkBitmapRegionCanvas.h b/src/android/SkBitmapRegionCanvas.h
index 2edbf1ff3bddd9d34eaf7f404a5fcc45afc79ba5..c01f96be3c4306c1112ed2a71adf9ef96bd72ff8 100644
--- a/src/android/SkBitmapRegionCanvas.h
+++ b/src/android/SkBitmapRegionCanvas.h
@@ -14,8 +14,16 @@
  * an SkCanvas.  It uses the scanline decoder to subset the height.  It then
  * will subset the width and scale by drawing to an SkCanvas.
  */
-// FIXME (msarett): This implementation does not support WEBP, because WEBP
-// does not have a scanline decoder.
+// FIXME: This class works well as a performance/quality comparison for
+//        SkBitmapRegionCodec, but it lacks several capabilities that are
+//        required by BitmapRegionDecoder in Android.
+//        (1) WEBP decodes - because SkWebpCodec does not have a scanline
+//            decoder.
+//        (2) Decodes to kGray8 and kIndex8.
+//        (3) Decodes to kUnpremul.
+//        (4) Correcting an invalid dstColorType.  For example, if the
+//            client requests kRGB_565 for a non-opaque image, rather than
+//            fail, we need to go ahead and decode to kN32.
 class SkBitmapRegionCanvas : public SkBitmapRegionDecoder {
 public: