[BlinkGenPropertyTrees] Rebaseline compositing/overflow/nested-border-radius-clipping.html

The BGPT result is correct, though with subpixel differences along
rounded corners.

Before BGPT, the bottom-left corner was not clipped with rounded
border.

Change-Id: I17fd469f5ed29354a6d1dcd76970b07c88bbe4ea
Reviewed-on: https://chromium-review.googlesource.com/c/1366768
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614757}

third_party/blink/web_tests/TestExpectations

@@ -227,10 +227,6 @@ crbug.com/619427 [ Linux ] virtual/composite-after-paint/fast/overflow/overflow-
 crbug.com/771643 external/wpt/css/css-backgrounds/background-attachment-local/attachment-local-clipping-color-5.html [ Failure ]
 crbug.com/771643 external/wpt/css/css-backgrounds/background-attachment-local/attachment-local-clipping-image-5.html [ Failure ]
 
-# Difficult ancestor clip mask issue.
-crbug.com/771643 compositing/overflow/nested-border-radius-clipping.html [ Failure ]
-crbug.com/771643 virtual/prefer_compositing_to_lcd_text/compositing/overflow/nested-border-radius-clipping.html [ Failure ]
-
 # Fails due to flaws in the SPv1 architecture. Can be fixed with composite-after-paint.
 crbug.com/862483 compositing/overflow/scrollbar-layer-placement-negative-z-index-child.html [ Failure ]
 crbug.com/862483 virtual/prefer_compositing_to_lcd_text/compositing/overflow/scrollbar-layer-placement-negative-z-index-child.html [ Failure ]