Fix overflow caught by ASAN.

src/codec/SkBmpCodec.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.
  */
 #ifndef SkBmpCodec_DEFINED
 #define SkBmpCodec_DEFINED
 
 #include "SkCodec.h"
@@ skipping 63 matching lines @@
      *
      * @param y      Iterates from 0 to height, indicating the current row.
      * @param height The height of the current subset of the image that we are
      *               decoding.  This is generally equal to the full height
      *               when we want to decode the full or one when we are
      *               sampling.
      */
     int32_t getDstRow(int32_t y, int32_t height) const;
 
     /*
-     * Compute the number of colors in the color table
-     */
-    uint32_t computeNumColors(uint32_t numColors);
-
-    /*
      * Accessors used by subclasses
      */
     uint16_t bitsPerPixel() const { return fBitsPerPixel; }
     SkScanlineOrder onGetScanlineOrder() const override { return fRowOrder; }
 
     /*
      * To be overriden by bmp subclasses, which provide unique implementations.
      * Performs subclass specific setup.
      *
      * @param dstInfo         Contains output information.  Height specifies
@@ skipping 44 matching lines @@
 
     // TODO(msarett): Override default skipping with something more clever.
 
     const uint16_t          fBitsPerPixel;
     const SkScanlineOrder   fRowOrder;
 
     typedef SkCodec INHERITED;
 };
 
 #endif