virtual/prefer_compositing_to_lcd_text/scrollbars/hidden-scrollbars-invisible.html fails with --additional-driver-flag=--enable-blink-gen-property-trees

This will start failing after https://chromium-review.googlesource.com/c/chromium/src/+/1226264 because we will no longer reset the LayerTreeHost on every frame.

Resetting the PaintedScrollbarLayer's LayerTreeHost has the effect of resetting the thumb resource which is why this test was working before.