fixing onSkipScanlines png error

There was a bug in onSkipScanlines where NULL was being passed instead of the SrcRow to png_read_rows.
This caused SkipScanlines to appear to be skipping, as fCurrScanline was updated and SkipScanlines returned success, however png_read_rows was not actually reading anything, and no lines were skipped.

Review URL: https://codereview.chromium.org/1159853003
1 file changed