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Status: Assigned
EstimatedDays: ----
NextAction: ----
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Pri: 3
Type: Bug

issue 836897

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Issue 921105: [BGPT] virtual/threaded/animations/skew-notsequential-compositor.html is flaky

Reported by, Jan 11 Project Member

Issue description

Filing this bug a little ahead of time, but with the fix for  issue 912574 , virtual/threaded/animations/skew-notsequential-compositor.html becomes flaky on BGPT (looks like AA difference).

I will be copying information from that issue over, but the gist is that in the non-flaky case there appears to be an additional commit before the test finishes, and somehow that is producing different output from the flaky case which doesn't have a final commit (based on dumping layer tree via --additional-driver-flag=--vmodule=layer_tree_host=3)

Reproduction (post  issue 912574  CL):

python third_party/blink/tools/ --additional-driver-flag=--vmodule=layer_tree_host=3 --repeat-each=100 --exit-after-n-failures=1 virtual/threaded/animations/skew-notsequential-compositor.html

Comment 1 by, Jan 11

Attached are cleaned up logs from runs of this test before the CL, after the CL (not flaky), and after the CL (flaky).
29.2 KB View Download
54.6 KB View Download
55.2 KB View Download

Comment 2 by, Jan 11

Adding rAFs to the test also make it non-flaky (as far as I can tell across 100 runs, which usually reproduces the flake), which further helps the theory of 'for some reason the commit changes something'.

$ git diff
diff --git a/third_party/blink/web_tests/animations/skew-notsequential-compositor.html b/third_party/blink/web_tests/animations/skew-notsequential-compositor.html
index 8f6925b44f3f..fd2d8cb22283 100644
--- a/third_party/blink/web_tests/animations/skew-notsequential-compositor.html
+++ b/third_party/blink/web_tests/animations/skew-notsequential-compositor.html
@@ -30,3 +30,17 @@ div {
 <div id="test"></div>
+if (window.testRunner) {
+  testRunner.waitUntilDone();
+requestAnimationFrame(function() {
+  requestAnimationFrame(function() {
+    if (window.testRunner) {
+      testRunner.notifyDone();
+    }
+  });

Comment 3 by, Jan 11

Project Member
The following revision refers to this bug:

commit 2a511d649f39d3f59cecf4731803a2179ea0c322
Author: Stephen McGruer <>
Date: Fri Jan 11 20:30:06 2019

Reland "[BlinkGenPropertyTrees] Fix ElementIsAnimatingChanged logic"

This relands the commit b0eab4a3e36612417196e6766d7a770f675169c4 from

The only change is to mark virtual/threaded/animations/skew-notsequential-compositor.html
as flaky; it has been decided that it is worth landing the CL anyway
and investigating the flakiness afterwards.,

Bug:  912574 , 921105
Change-Id: I93dfc5db4056e3567f99254f28b1072a66c4f532
Reviewed-by: Stephen McGruer <>
Reviewed-by: Philip Rogers <>
Commit-Queue: Stephen McGruer <>
Cr-Commit-Position: refs/heads/master@{#622123}

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