Implement onSkipScanlines() for bmp and wbmp

src/codec/SkBmpRLECodec.h

Index: src/codec/SkBmpRLECodec.h
diff --git a/src/codec/SkBmpRLECodec.h b/src/codec/SkBmpRLECodec.h
index e319a71052dd04d0b3371e9452a0306cd7d17466..2ddf8d8b90c9a97a4d51677e7df52cc4f73aa782 100644
--- a/src/codec/SkBmpRLECodec.h
+++ b/src/codec/SkBmpRLECodec.h
@@ -84,9 +84,14 @@ private:
                      const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
                      uint8_t red, uint8_t green, uint8_t blue);
 
+    /*
+     * If dst is NULL, this is a signal to skip the rows.
+     */
     int decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes,
             const Options& opts) override;
 
+    bool skipRows(int count) override;
+
     SkSampler* getSampler(bool createIfNecessary) override;
 
     SkAutoTUnref<SkColorTable>          fColorTable;    // owned