Add subsetting to SkScaledCodec

src/codec/SkBmpCodec.h

Index: src/codec/SkBmpCodec.h
diff --git a/src/codec/SkBmpCodec.h b/src/codec/SkBmpCodec.h
index 65662ff1f869df3a655799f93e73598ed57a4a6a..7da396ca8cb828cce9d8df0dac29d51bebecb314 100644
--- a/src/codec/SkBmpCodec.h
+++ b/src/codec/SkBmpCodec.h
@@ -89,6 +89,12 @@ protected:
      * Accessors used by subclasses
      */
     uint16_t bitsPerPixel() const { return fBitsPerPixel; }
+
+    int subsetLeft() const { return fSubsetLeft; }
+    int subsetWidth() const {return fSubsetWidth; }
+
+private:
+
     SkScanlineOrder onGetScanlineOrder() const override { return fRowOrder; }
 
     /*
@@ -110,8 +116,6 @@ protected:
             const SkCodec::Options& options, SkPMColor inputColorPtr[],
             int* inputColorCount) = 0;
 
-private:
-
     /*
      * Creates a bmp decoder
      * Reads enough of the stream to determine the image format
@@ -137,13 +141,16 @@ private:
             const Options& opts) = 0;
 
     Result onStartScanlineDecode(const SkImageInfo& dstInfo, const SkCodec::Options&,
-            SkPMColor inputColorPtr[], int* inputColorCount) override;
+            SkPMColor inputColorPtr[], int* inputColorCount, int subsetLeft, int subsetWidth)
+            override;
 
     int onGetScanlines(void* dst, int count, size_t rowBytes) override;
 
     // TODO(msarett): Override default skipping with something more clever.
 
     const uint16_t          fBitsPerPixel;
+    int                     fSubsetLeft;
+    int                     fSubsetWidth;
     const SkScanlineOrder   fRowOrder;
 
     typedef SkCodec INHERITED;