Implement onSkipScanlines() for bmp and wbmp

src/codec/SkBmpCodec.cpp

 /*
  * 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 "SkBmpCodec.h"
 #include "SkBmpMaskCodec.h"
 #include "SkBmpRLECodec.h"
@@ skipping 528 matching lines @@
         return codec;
     }
     return nullptr;
 }
 
 SkBmpCodec::SkBmpCodec(const SkImageInfo& info, SkStream* stream,
         uint16_t bitsPerPixel, SkCodec::SkScanlineOrder rowOrder)
     : INHERITED(info, stream)
     , fBitsPerPixel(bitsPerPixel)
     , fRowOrder(rowOrder)
+    , fSrcRowBytes(SkAlign4(compute_row_bytes(info.width(), fBitsPerPixel)))
 {}
 
 bool SkBmpCodec::onRewind() {
     return SkBmpCodec::ReadHeader(this->stream(), this->inIco(), nullptr);
 }
 
 int32_t SkBmpCodec::getDstRow(int32_t y, int32_t height) const {
     if (SkCodec::kTopDown_SkScanlineOrder == fRowOrder) {
         return y;
     }
@@ skipping 11 matching lines @@
     return prepareToDecode(dstInfo, options, inputColorPtr, inputColorCount);
 }
 
 int SkBmpCodec::onGetScanlines(void* dst, int count, size_t rowBytes) {
     // Create a new image info representing the portion of the image to decode
     SkImageInfo rowInfo = this->dstInfo().makeWH(this->dstInfo().width(), count);
 
     // Decode the requested rows
     return this->decodeRows(rowInfo, dst, rowBytes, this->options());
 }
+
+bool SkBmpCodec::skipRows(int count) {
+    const size_t bytesToSkip = count * fSrcRowBytes;
+    return this->stream()->skip(bytesToSkip) == bytesToSkip;
+}
+
+bool SkBmpCodec::onSkipScanlines(int count) {
+    return this->skipRows(count);
+}