Add subsetting to SkScaledCodec

tools/SkBitmapRegionDecoderInterface.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 SkBitmapRegionDecoder_DEFINED
 #define SkBitmapRegionDecoder_DEFINED
 
 #include "SkBitmap.h"
 #include "SkStream.h"
 
 /*
  * This class aims to provide an interface to test multiple implementations of
  * SkBitmapRegionDecoder.
  */
 class SkBitmapRegionDecoderInterface {
 public:
 
     enum Strategy {
         kCanvas_Strategy,   // Draw to the canvas, uses SkCodec
         kOriginal_Strategy, // Sampling, uses SkImageDecoder
-        // TODO (msarett): Add strategy for SkScaledCodec
+        kCodec_Strategy,    // Uses SkScaledCodec for scaling and subsetting
     };
 
     /*
      * @param stream   Encoded image stream, takes ownership
      * @param strategy Strategy used for scaling and subsetting
      * @return         Tries to create an SkBitmapRegionDecoder, returns NULL
      *                 on failure
      */
     static SkBitmapRegionDecoderInterface* CreateBitmapRegionDecoder(
             SkStreamRewindable* stream, Strategy strategy);
@@ skipping 15 matching lines @@
      *                   decoding to this color type.
      *                   The old kOriginal_Strategy will decode to a default color type
      *                   if this color type is unsupported.
      * @return           Pointer to a bitmap of the decoded region on success, NULL on
      *                   failure.
      */
     virtual SkBitmap* decodeRegion(int start_x, int start_y, int width,
                                    int height, int sampleSize,
                                    SkColorType colorType) = 0;
 
+    /*
+     * @param  Requested destination color type
+     * @return true if we support the requested color type and false otherwise
+     */
+    virtual bool conversionSupported(SkColorType colorType) = 0;
+
     int width() const { return fWidth; }
     int height() const { return fHeight; }
 
     virtual ~SkBitmapRegionDecoderInterface() {}
 
 protected:
 
     SkBitmapRegionDecoderInterface(int width, int height)
         : fWidth(width)
         , fHeight(height)
     {}
 
 private:
     const int fWidth;
     const int fHeight;
 };
 
 #endif