Fix bmp RLE "bug" and add invalid image test to CodexTest

src/codec/SkBmpRLECodec.h

Index: src/codec/SkBmpRLECodec.h
diff --git a/src/codec/SkBmpRLECodec.h b/src/codec/SkBmpRLECodec.h
index f1f1ae97d8b2ba596c781592d8315935537dc7ec..5432b6402a62ba3e2045b71b71d6d1457e498312 100644
--- a/src/codec/SkBmpRLECodec.h
+++ b/src/codec/SkBmpRLECodec.h
@@ -56,6 +56,15 @@ private:
     bool initializeStreamBuffer();
 
     /*
+     * It is possible for an encoded image stream to contain more encoded data than
+     * it reports that it has.  Before signalling kIncompleteInput, we should check

[scroggo, 2015/08/12 14:14:30]

Maybe this should say something like:

Before signaling kIncompleteInput, we call this method to attempt to load the
stream buffer with any additional data.

[msarett, 2015/08/12 15:01:24]

Agreed.  Done.

+     * if we can reset the stream buffer with additional data.
+     *
+     * @return the number of bytes remaining in the new stream buffer

[scroggo, 2015/08/12 14:14:30]

nit: In my mind, the stream buffer itself is not new - just the data

[msarett, 2015/08/12 15:01:24]

Yeah agreed.  I need the remove the work "new" from all of my comments.

+     */
+    size_t resetStreamBuffer();

[scroggo, 2015/08/12 14:14:30]

I'm not a big fan of the name. It doesn't really explain its purpose. Maybe it
should be something like checkForMoreData?or checkForExtraData?

[msarett, 2015/08/12 15:01:24]

I like checkForMoreData.

+
+    /*
      * Set an RLE pixel using the color table
      */
     void setPixel(void* dst, size_t dstRowBytes,