Add subsetting to SkScaledCodec

tools/SkBitmapRegionCodec.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.
  */
 
 #include "SkBitmap.h"
 #include "SkBitmapRegionDecoderInterface.h"
-#include "SkImageDecoder.h"
-#include "SkTemplates.h"
+#include "SkCodec.h"
 
 /*
- * This class aims to duplicate the current implementation of
- * SkBitmapRegionDecoder in Android.
+ * This class implements SkBitmapRegionDecoder using an SkScaledCodec.
  */
-class SkBitmapRegionSampler : public SkBitmapRegionDecoderInterface {
+class SkBitmapRegionCodec : public SkBitmapRegionDecoderInterface {
 public:
 
     /*
-     * Takes ownership of pointer to decoder
+     * Takes ownership of pointer to codec
      */
-    SkBitmapRegionSampler(SkImageDecoder* decoder, int width, int height);
+    SkBitmapRegionCodec(SkCodec* codec);
 
     /*
-     * Three differences from the Android version:
+     * Three key 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 conversionSupported(SkColorType colorType) override;
+
 private:
 
-    SkAutoTDelete<SkImageDecoder> fDecoder;
+    SkAutoTDelete<SkCodec> fCodec;
 
     typedef SkBitmapRegionDecoderInterface INHERITED;
 
 };