[BlinkGenPropertyTrees] Pass fast/canvas/synchronous-create-pattern.html

This test is now passing with BGPT and does not need a failing expectation:
  fast/canvas/synchronous-create-pattern.html

Bug: 853947

Cq-Include-Trybots: luci.chromium.try:linux-blink-gen-property-trees;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Id5bdba3ce5de2b6bb8d10d3a9d9d23bf1095a5dc
Reviewed-on: https://chromium-review.googlesource.com/1146778Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577282}

third_party/WebKit/LayoutTests/FlagExpectations/enable-blink-gen-property-trees

@@ -407,9 +407,6 @@ Bug(none) fast/clip/overflow-border-radius-composited.html [ Failure ]
 # Something wrong with vertical-rl scrollbars
 crbug.com/853945 fast/block/positioning/vertical-rl/002.html [ Failure ]
 
-# Something with the pattern is wrong. Needs investigation.
-crbug.com/853947 fast/canvas/synchronous-create-pattern.html [ Failure ]
-
 # Composited multicolumn paints differently.
 crbug.com/854192 fast/multicol/composited-layer-nested.html [ Failure ]
 crbug.com/854192 fast/multicol/vertical-rl/composited-relpos-overlapping-will-change.html [ Failure ]