Implement onSkipScanlines() for bmp and wbmp

src/codec/SkWbmpCodec.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 SkCodec_wbmp_DEFINED
 #define SkCodec_wbmp_DEFINED
 
@@ skipping 34 matching lines @@
 
     SkWbmpCodec(const SkImageInfo&, SkStream*);
 
     const size_t                 fSrcRowBytes;
 
     // Used for scanline decodes:
     SkAutoTDelete<SkSwizzler>    fSwizzler;
     SkAutoTUnref<SkColorTable>   fColorTable;
     SkAutoTMalloc<uint8_t>       fSrcBuffer;
 
-    // FIXME: Override onSkipScanlines to avoid swizzling.
     int onGetScanlines(void* dst, int count, size_t dstRowBytes) override;
+    bool onSkipScanlines(int count) override;
     Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
             SkPMColor inputColorTable[], int* inputColorCount) override;
 
     typedef SkCodec INHERITED;
 };
 
 #endif  // SkCodec_wbmp_DEFINED