Allow ico decoder to decode PNG sub-images.

include/core/SkImageDecoder.h

Index: include/core/SkImageDecoder.h
diff --git a/include/core/SkImageDecoder.h b/include/core/SkImageDecoder.h
index 360f03acb6304022b949b3d4708456c336b227c4..9ef2e41e1c83505979f77d95ab8e839572ae1a68 100644
--- a/include/core/SkImageDecoder.h
+++ b/include/core/SkImageDecoder.h
@@ -395,7 +395,17 @@ protected:
                     int dstX, int dstY, int width, int height,
                     int srcX, int srcY);
 
+    /**
+     *  Copy all fields on this decoder to the other decoder. Used by subclasses
+     *  to decode a subimage using a different decoder, but with the same settings.
+     */
+    void copyFieldsToOther(SkImageDecoder* other);
 
+    /**
+     *  Return the default preference being used by the current or latest call to
+     *  decode.
+     */
+    SkBitmap::Config getDefaultPref() { return fDefaultPref; }
 
     /** Can be queried from within onDecode, to see if the user (possibly in
         a different thread) has requested the decode to cancel. If this returns