Add subsetting to SkScaledCodec

include/codec/SkScaledCodec.h

Index: include/codec/SkScaledCodec.h
diff --git a/include/codec/SkScaledCodec.h b/include/codec/SkScaledCodec.h
index 6e569d5d381b532d11ef6b1962eba1d3b311c39c..e9ab4a23ce468c5ac4311a0987ea3c6bb5e6556f 100644
--- a/include/codec/SkScaledCodec.h
+++ b/include/codec/SkScaledCodec.h
@@ -38,7 +38,7 @@ public:
         return true;   
     }
 
-    static void ComputeSampleSize(const SkImageInfo& dstInfo, const SkImageInfo& srcInfo,
+    static void ComputeSampleSize(const SkISize& dstSize, const SkISize& srcSize,
                                   int* sampleSizeX, int* sampleSizeY);
 
 protected:
@@ -47,6 +47,8 @@ protected:
      */
     SkISize onGetScaledDimensions(float desiredScale) const override;
 
+    bool onGetScaledSubsetDimensions(float desiredScale, Options* options) const override;
+
     Result onGetPixels(const SkImageInfo&, void*, size_t, const Options&, SkPMColor*, int*, int*)
             override;
     SkEncodedFormat onGetEncodedFormat() const override {
@@ -63,6 +65,13 @@ protected:
 
 private:
 
+    Result nativeDecode(const SkImageInfo& scaledInfo, void* dst, size_t rowBytes,
+            const SkIRect& scaledSubsetRect, ZeroInitialized zeroInit, int* rowsDecoded);
+
+    Result sampledDecode(const SkImageInfo& decodeInfo, void* dst, size_t rowBytes,
+            const SkIRect& subsetRect, const SkIRect& scaledSubsetRect, int sampleX, int sampleY,
+            ZeroInitialized zeroInit, int* rowsDecoded);
+
     SkAutoTDelete<SkCodec> fCodec;
 
     explicit SkScaledCodec(SkCodec*);