Fill incomplete images in SkCodec parent class

src/codec/SkBmpCodec.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 SkBmpCodec_DEFINED
 #define SkBmpCodec_DEFINED
 
 #include "SkCodec.h"
@@ skipping 64 matching lines @@
      *
      * @param y      Iterates from 0 to height, indicating the current row.
      * @param height The height of the current subset of the image that we are
      *               decoding.  This is generally equal to the full height
      *               when we want to decode the full or one when we are
      *               sampling.
      */
     int32_t getDstRow(int32_t y, int32_t height) const;
 
     /*
-     * Get the destination row to start filling from
-     * Used to fill the remainder of the image on incomplete input for bmps
-     * This is tricky since bmps may be kTopDown or kBottomUp.  For kTopDown,
-     * we start filling from where we left off, but for kBottomUp we start
-     * filling at the top of the image.
-     */
-    void* getDstStartRow(void* dst, size_t dstRowBytes, int32_t y) const;
-
-    /*
      * Compute the number of colors in the color table
      */
     uint32_t computeNumColors(uint32_t numColors);
 
     /*
      * Accessors used by subclasses
      */
     uint16_t bitsPerPixel() const { return fBitsPerPixel; }
     SkScanlineOrder onGetScanlineOrder() const override { return fRowOrder; }
 
@@ skipping 30 matching lines @@
      * onGetPixels() uses this for full image decodes.
      * SkScaledCodec::onGetPixels() uses the scanline decoder to call this with
      * dstInfo.height() = 1, in order to implement sampling.
      * A potential future use is to allow the caller to decode a subset of the
      * lines in the image.
      *
      * @param dstInfo     Contains output information.  Height specifies the
      *                    number of rows to decode at this time.
      * @param dst         Memory location to store output pixels
      * @param dstRowBytes Bytes in a row of the destination
+     * @return            Number of rows successfully decoded
      */
-    virtual Result decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes,
+    virtual uint32_t decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes,
             const Options& opts) = 0;
 
     Result onStartScanlineDecode(const SkImageInfo& dstInfo, const SkCodec::Options&,
             SkPMColor inputColorPtr[], int* inputColorCount) override;
 
-    Result onGetScanlines(void* dst, int count, size_t rowBytes) override;
-
-    int onNextScanline() const override;
+    uint32_t onGetScanlines(void* dst, int count, size_t rowBytes) override;
 
     // TODO(msarett): Override default skipping with something more clever.
 
     const uint16_t          fBitsPerPixel;
     const SkScanlineOrder   fRowOrder;
 
     typedef SkCodec INHERITED;
 };
 
 #endif