http/tests/devtools/layers/layer-compositing-reasons.js is passing

The previous failures were just because the test is slow. The runs have
been green since it was marked slow.

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests%20(with%20patch)&tests=http%2Ftests%2Fdevtools%2Flayers%2Flayer-compositing-reasons.js
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=http%2Ftests%2Fdevtools%2Flayers%2Flayer-compositing-reasons.js

TBR=wangxianzhu@chromium.org

Bug: 859169
Change-Id: I3e798d06da032b0570d0b1f0cd0003153891b869
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2042529
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739150}

third_party/blink/web_tests/TestExpectations

@@ -6323,9 +6323,6 @@ crbug.com/1034789 [ Mac ] http/tests/security/frameNavigation/xss-ALLOWED-parent
 crbug.com/1034789 [ Mac10.13 ] virtual/threaded/fast/scroll-snap/snap-to-target-on-layout-change.html [ Pass Timeout ]
 crbug.com/1034789 [ Mac10.13 ] external/wpt/pointerevents/pointerevent_coalesced_events_attributes.html [ Pass Failure ]
 
-# Sheriff 2019-12-18
-crbug.com/859169 http/tests/devtools/layers/layer-compositing-reasons.js [ Pass Failure ]
-
 # Sheriff 2019-12-23
 crbug.com/1036626 http/tests/devtools/tracing/tracing-record-input-events.js [ Pass Failure ]
 crbug.com/1036626 virtual/threaded/http/tests/devtools/tracing/tracing-record-input-events.js [ Pass Failure ]