Implement onSkipScanlines() for bmp and wbmp

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 @@
      *               when we want to decode the full or one when we are
      *               sampling.
      */
     int32_t getDstRow(int32_t y, int32_t height) const;
 
     /*
      * Accessors used by subclasses
      */
     uint16_t bitsPerPixel() const { return fBitsPerPixel; }
     SkScanlineOrder onGetScanlineOrder() const override { return fRowOrder; }
+    size_t srcRowBytes() const { return fSrcRowBytes; }
 
     /*
      * To be overriden by bmp subclasses, which provide unique implementations.
      * Performs subclass specific setup.
      *
      * @param dstInfo         Contains output information.  Height specifies
      *                        the total number of rows that will be decoded.
      * @param options         Additonal options to pass to the decoder.
      * @param inputColorPtr   Client-provided memory for a color table.  Must
      *                        be enough for 256 colors.  This will be
@@ skipping 26 matching lines @@
      *
      * @param dstInfo     Contains output information.  Height specifies the
      *                    number of rows to decode at this time.
      * @param dst         Memory location to store output pixels
      * @param dstRowBytes Bytes in a row of the destination
      * @return            Number of rows successfully decoded
      */
     virtual int decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes,
             const Options& opts) = 0;
 
+    virtual bool skipRows(int count);
+
     Result onStartScanlineDecode(const SkImageInfo& dstInfo, const SkCodec::Options&,
             SkPMColor inputColorPtr[], int* inputColorCount) override;
 
     int onGetScanlines(void* dst, int count, size_t rowBytes) override;
 
-    // TODO(msarett): Override default skipping with something more clever.
+    bool onSkipScanlines(int count) override;
 
     const uint16_t          fBitsPerPixel;
     const SkScanlineOrder   fRowOrder;
+    const size_t            fSrcRowBytes;
 
     typedef SkCodec INHERITED;
 };
 
 #endif