fast/repaint/obscured-background-no-repaint.html is flaky on Linux/Win dbg

BUG=622368

Review URL: https://codereview.chromium.org/2090103002 .

Cr-Commit-Position: refs/heads/master@{#401322}
diff --git a/third_party/WebKit/LayoutTests/TestExpectations b/third_party/WebKit/LayoutTests/TestExpectations
index 6e7e23e..a90660d 100644
--- a/third_party/WebKit/LayoutTests/TestExpectations
+++ b/third_party/WebKit/LayoutTests/TestExpectations
@@ -1511,6 +1511,8 @@
 # Note: this test was previously marked as slow on Debug builds. Skipping until crash is fixed
 crbug.com/619978 fast/css/giant-stylesheet-crash.html [ Skip ]
 
+crbug.com/622368 [ Linux Win Debug ] fast/repaint/obscured-background-no-repaint.html [ Pass Failure ]
+
 crbug.com/621892 css3/filters/effect-brightness-clamping-hw.html [ Pass Failure ]
 crbug.com/621892 css3/filters/effect-brightness-hw.html [ Pass Failure ]
 crbug.com/621892 css3/filters/effect-hue-rotate-hw.html [ Pass Failure ]