Add subsetting to SkScaledCodec

src/codec/SkCodec_wbmp.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 14 matching lines @@
 protected:
     SkEncodedFormat onGetEncodedFormat() const override;
     Result onGetPixels(const SkImageInfo&, void*, size_t,
                        const Options&, SkPMColor[], int*, int*) override;
     bool onRewind() override;
 private:
     /*
      * Returns a swizzler on success, nullptr on failure
      */
     SkSwizzler* initializeSwizzler(const SkImageInfo& info, const SkPMColor* ctable,
-                                   const Options& opts);
+                                   const Options& opts, int subsetLeft, int subsetHeight);
     SkSampler* getSampler(bool createIfNecessary) override { return fSwizzler; }
 
     /*
      * Read a src row from the encoded stream
      */
     bool readRow(uint8_t* row);
 
     SkWbmpCodec(const SkImageInfo&, SkStream*);
 
     const size_t                 fSrcRowBytes;
     SkAutoTDelete<SkSwizzler>    fSwizzler;
 
     // Used for scanline decodes:
     SkAutoTUnref<SkColorTable>   fColorTable;
     SkAutoTMalloc<uint8_t>       fSrcBuffer;
 
     // FIXME: Override onSkipScanlines to avoid swizzling.
     int onGetScanlines(void* dst, int count, size_t dstRowBytes) override;
     Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
-            SkPMColor inputColorTable[], int* inputColorCount) override;
+            SkPMColor inputColorTable[], int* inputColorCount, int subsetLeft, int subsetWidth)
+            override;
 
     typedef SkCodec INHERITED;
 };
 
 #endif  // SkCodec_wbmp_DEFINED