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

src/codec/SkBmpRLECodec.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBmpCodec.h"
 #include "SkColorTable.h"
 #include "SkImageInfo.h"
@@ skipping 38 matching lines @@
 
     /*
      * Creates the color table
      * Sets colorCount to the new color count if it is non-NULL
      */
     bool createColorTable(int* colorCount);
 
     bool initializeStreamBuffer();
 
     /*
+     * Before signalling kIncompleteInput, we should attempt to load the
+     * stream buffer with additional data.
+     *
+     * @return the number of bytes remaining in the stream buffer after
+     *         attempting to read more bytes from the stream
+     */
+    size_t checkForMoreData();
+
+    /*
      * Set an RLE pixel using the color table
      */
     void setPixel(void* dst, size_t dstRowBytes,
                   const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
                   uint8_t index);
     /*
      * Set an RLE24 pixel from R, G, B values
      */
     void setRGBPixel(void* dst, size_t dstRowBytes,
                      const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
                      uint8_t red, uint8_t green, uint8_t blue);
 
     /*
      * Performs the bitmap decoding for RLE input format
      */
     Result decode(const SkImageInfo& dstInfo, void* dst,
                   size_t dstRowBytes, const Options& opts);
 
     SkAutoTUnref<SkColorTable>          fColorTable;    // owned
     const uint32_t                      fNumColors;
     const uint32_t                      fBytesPerColor;
     const uint32_t                      fOffset;
     SkAutoTDeleteArray<uint8_t>         fStreamBuffer;
     size_t                              fRLEBytes;
     uint32_t                            fCurrRLEByte;
 
     typedef SkBmpCodec INHERITED;
 };