Add subsetting to SkScaledCodec

src/codec/SkMaskSwizzler.h

Index: src/codec/SkMaskSwizzler.h
diff --git a/src/codec/SkMaskSwizzler.h b/src/codec/SkMaskSwizzler.h
index 794dcd16e498e8948a1065ba6e29bb31bdc8361a..14e2b4f8f1a476a5a4aa8c2d865ce88dec0f9fff 100644
--- a/src/codec/SkMaskSwizzler.h
+++ b/src/codec/SkMaskSwizzler.h
@@ -27,7 +27,9 @@ public:
     static SkMaskSwizzler* CreateMaskSwizzler(const SkImageInfo& dstInfo,
                                               const SkImageInfo& srcInfo,
                                               SkMasks* masks,
-                                              uint32_t bitsPerPixel);
+                                              uint32_t bitsPerPixel,
+                                              int subsetLeft,
+                                              int subsetWidth);
 
     /*
      * Swizzle a row
@@ -39,20 +41,18 @@ private:
     /*
      * Row procedure used for swizzle
      */
-    typedef SkSwizzler::ResultAlpha (*RowProc)(
-            void* dstRow, const uint8_t* srcRow, int width,
+    typedef SkSwizzler::ResultAlpha (*RowProc)(void* dstRow, const uint8_t* srcRow, int width,
             SkMasks* masks, uint32_t startX, uint32_t sampleX);
 
     /*
      * Constructor for mask swizzler
      */
-    SkMaskSwizzler(const SkImageInfo& info, SkMasks* masks, RowProc proc,
-            uint32_t sampleX);
+    SkMaskSwizzler(SkMasks* masks, RowProc proc, uint32_t width, uint32_t sampleX, uint32_t startX);
 
     // Fields
-    const SkImageInfo& fDstInfo;
     SkMasks*           fMasks;       // unowned
     const RowProc      fRowProc;
+    const uint32_t     fWidth;
     const uint32_t     fSampleX;
     const uint32_t     fStartX;
 };