Add nanobench tests for BitmapRegionDecoder

dm/DMSrcSink.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 DMSrcSink_DEFINED
 #define DMSrcSink_DEFINED
 
@@ skipping 126 matching lines @@
         kFullImage_Mode,
         // Splits the image into multiple regions using a divisor and decodes the regions
         // separately.  Also, this test adds a border of a few pixels to each of the regions
         // that it is decoding.  This tests the behavior when a client asks for a region that
         // does not fully fit in the image.
         kDivisor_Mode,
     };
 
     BRDSrc(Path, SkBitmapRegionDecoderInterface::Strategy, Mode, CodecSrc::DstColorType, uint32_t);
 
-    static float GetScale(uint32_t sampleSize) { return 1.0f / (float) sampleSize; }
-
     Error draw(SkCanvas*) const override;
     SkISize size() const override;
     Name name() const override;
     bool veto(SinkFlags) const override;
 private:
     Path                                     fPath;
     SkBitmapRegionDecoderInterface::Strategy fStrategy;
     Mode                                     fMode;
     CodecSrc::DstColorType                   fDstColorType;
     uint32_t                                 fSampleSize;
@@ skipping 180 matching lines @@
 
 class ViaTwice : public Via {
 public:
     explicit ViaTwice(Sink* sink) : Via(sink) {}
     Error draw(const Src&, SkBitmap*, SkWStream*, SkString*) const override;
 };
 
 }  // namespace DM
 
 #endif//DMSrcSink_DEFINED