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
+     * if we can reset the stream buffer with additional data.
+     *
+     * @return the number of bytes remaining in the new stream buffer
+     */
+    size_t resetStreamBuffer();
+
+    /*
      * Set an RLE pixel using the color table
      */
     void setPixel(void* dst, size_t dstRowBytes,