Move all knowledge of X sampling into SkScaledCodec

include/codec/SkScaledCodec.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 SkScaledCodec_DEFINED
 #define SkScaledCodec_DEFINED
 
 #include "SkCodec.h"
 
 class SkStream;
 
 /**
  * This class implements scaling, by sampling scanlines in the y direction.
  * x-wise sampling is implemented in the swizzler, when getScanlines() is called.
  */
 class SkScaledCodec : public SkCodec {
 public:
     static SkCodec* NewFromStream(SkStream*);
     static SkCodec* NewFromData(SkData*);
 
     virtual ~SkScaledCodec();
 
-    /**
-     * returns whether a destination's dimensions are supported for down sampling
-     */
-    static bool DimensionsSupportedForSampling(const SkImageInfo& srcInfo, 
-                                               const SkImageInfo& dstInfo) {
-        // heights must be equal as no native y sampling is supported
-        if (dstInfo.height() != srcInfo.height()) {
-            return false;
-        }
-        // only support down sampling, dstWidth cannot be larger that srcWidth
-        if(dstInfo.width() > srcInfo.width()) {
-            return false;
-        }
-        return true;   
-    }
-
-    static void ComputeSampleSize(const SkImageInfo& dstInfo, const SkImageInfo& srcInfo,
+    static void ComputeSampleSize(const SkISize& dstDim, const SkISize& srcDim,
                                   int* sampleSizeX, int* sampleSizeY);
 
 protected:
     /**
      * Recommend a set of destination dimensions given a requested scale
      */
     SkISize onGetScaledDimensions(float desiredScale) const override;
+    bool onDimensionsSupported(const SkISize&) override;
 
     Result onGetPixels(const SkImageInfo&, void*, size_t, const Options&, SkPMColor*, int*)
             override;
     SkEncodedFormat onGetEncodedFormat() const override {
         return fCodec->getEncodedFormat();
     }
 
     bool onReallyHasAlpha() const override {
         return fCodec->reallyHasAlpha();
     }
 
 private:
 
     SkAutoTDelete<SkCodec> fCodec;
 
     explicit SkScaledCodec(SkCodec*);
 
     typedef SkCodec INHERITED;
 };
 #endif // SkScaledCodec_DEFINED