These tests have a small pixel snapping difference from non-bgpt:
compositing/overflow/composited-scroll-with-fractional-translation.html
virtual/prefer_compositing_to_lcd_text/compositing/overflow/composited-scroll-with-fractional-translation.html

See:
https://test-results.appspot.com/data/layout_results/mac10_12-blink-rel/1351/webkit_layout_tests%20%28with%20patch%29/layout-test-results/results.html