Refactor SkBitmapRegionDecoderInterface for Android

tools/SkBitmapRegionCanvas.h

Index: tools/SkBitmapRegionCanvas.h
diff --git a/tools/SkBitmapRegionCanvas.h b/tools/SkBitmapRegionCanvas.h
index f82e9fa77a941b01dee6d746d2a2fb02006ea40e..ba3fa4563d947d14e6bb098c942b4f1846ced230 100644
--- a/tools/SkBitmapRegionCanvas.h
+++ b/tools/SkBitmapRegionCanvas.h
@@ -24,22 +24,24 @@ public:
      */
     SkBitmapRegionCanvas(SkCodec* decoder);
 
-    /*
-     * Three differences from the Android version:
-     *     Returns a Skia bitmap instead of an Android bitmap.
-     *     Android version attempts to reuse a recycled bitmap.
-     *     Removed the options object and used parameters for color type and
-     *     sample size.
-     */
-    SkBitmap* decodeRegion(int start_x, int start_y, int width, int height,
-                           int sampleSize, SkColorType prefColorType) override;
+    bool prepareRegion(const SkIRect& desiredSubset, int sampleSize,
+            SkColorType colorType, bool requireUnpremul, SkImageInfo* outSize) override;
 
-    bool conversionSupported(SkColorType colorType) override;
+    bool decodeRegion(SkBitmap& bitmap) override;
 
 private:
 
     SkAutoTDelete<SkCodec> fDecoder;
 
+    // Fields set by prepareRegion()
+    int         fOutX;       // Offset of decoded pixels in output bitmap
+    int         fOutY;       // Offset of decoded pixels in output bitmap
+    SkImageInfo fOutInfo;    // Image properties for output bitmap
+    SkImageInfo fDecodeInfo; // Image properties for fDecoder
+    int         fSampleSize; // Integer downscale factor
+    SkIRect     fSubset;     // Subset of the original image to decode
+    SubsetType  fSubsetType;
+
     typedef SkBitmapRegionDecoderInterface INHERITED;
 
 };