Provides multiple implementations of Android's SkBitmapRegionDecoder

tools/SkBitmapRegionCanvas.h

Index: tools/SkBitmapRegionCanvas.h
diff --git a/tools/SkBitmapRegionCanvas.h b/tools/SkBitmapRegionCanvas.h
new file mode 100644
index 0000000000000000000000000000000000000000..96631d70d3333bf99ca5cf23e26d1415def92ab9
--- /dev/null
+++ b/tools/SkBitmapRegionCanvas.h
@@ -0,0 +1,43 @@
+/*
+ * 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 "SkScanlineDecoder.h"
+
+/*
+ * This class implements SkBitmapRegionDecoder using an SkScanlineDecoder and
+ * an SkCanvas.  It uses the scanline decoder to subset the height.  It then
+ * will subset the width and scale by drawing to an SkCanvas.
+ */
+// FIXME (msarett): This implementation does not support WEBP, because WEBP
+// does not have a scanline decoder.
+class SkBitmapRegionCanvas : public SkBitmapRegionDecoderInterface {
+public:
+
+    /*
+     * Takes ownership of pointer to decoder
+     */
+    SkBitmapRegionCanvas(SkScanlineDecoder* 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;
+
+private:
+
+    SkAutoTDelete<SkScanlineDecoder> fDecoder;
+
+    typedef SkBitmapRegionDecoderInterface INHERITED;
+
+};