[macOS WK2] Layout Test tiled-drawing/scrolling/fast-scroll-iframe-latched-mainframe-with-handler.html is flaky.

[Matt Lewis]

The test tiled-drawing/scrolling/fast-scroll-iframe-latched-mainframe-with-handler.html is a flaky failure on macOS WK2.

This does not appear to be a recent regression on macOS Sierra, but recently started failing on El Capitan on 5/12.

Sierra:
https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=tiled-drawing%2Fscrolling%2Ffast-scroll-iframe-latched-mainframe-with-handler.html

https://build.webkit.org/builders/Apple%20Sierra%20Release%20WK2%20(Tests)/builds/1732
https://build.webkit.org/results/Apple%20Sierra%20Release%20WK2%20(Tests)/r217363%20(1732)/results.html

Diff:
--- /Volumes/Data/slave/sierra-release-tests-wk2/build/layout-test-results/tiled-drawing/scrolling/fast-scroll-iframe-latched-mainframe-with-handler-expected.txt
+++ /Volumes/Data/slave/sierra-release-tests-wk2/build/layout-test-results/tiled-drawing/scrolling/fast-scroll-iframe-latched-mainframe-with-handler-actual.txt
@@ -12,15 +12,15 @@
 (GraphicsLayer
   (anchor 0.00 0.00)
   (bounds 785.00 2266.00)
-  (visible rect 0.00, 70.00 785.00 x 600.00)
-  (coverage rect 0.00, 70.00 785.00 x 600.00)
+  (visible rect 0.00, 20.00 785.00 x 600.00)
+  (coverage rect 0.00, 20.00 785.00 x 600.00)
   (intersects coverage rect 1)
   (contentsScale 1.00)
   (children 1
     (GraphicsLayer
       (bounds 785.00 2266.00)
       (contentsOpaque 1)
-      (visible rect 0.00, 70.00 785.00 x 600.00)
+      (visible rect 0.00, 20.00 785.00 x 600.00)
       (coverage rect 0.00, 0.00 785.00 x 1800.00)
       (intersects coverage rect 1)
       (contentsScale 1.00)

El Capitan:
https://build.webkit.org/results/Apple%20El%20Capitan%20Debug%20WK2%20(Tests)/r216965%20(1168)/results.html
https://build.webkit.org/builders/Apple%20El%20Capitan%20Debug%20WK2%20(Tests)/builds/1168

diff:
--- /Volumes/Data/slave/elcapitan-debug-tests-wk2/build/layout-test-results/tiled-drawing/scrolling/fast-scroll-iframe-latched-mainframe-with-handler-expected.txt
+++ /Volumes/Data/slave/elcapitan-debug-tests-wk2/build/layout-test-results/tiled-drawing/scrolling/fast-scroll-iframe-latched-mainframe-with-handler-actual.txt
@@ -12,15 +12,15 @@
 (GraphicsLayer
   (anchor 0.00 0.00)
   (bounds 785.00 2266.00)
-  (visible rect 0.00, 70.00 785.00 x 600.00)
-  (coverage rect 0.00, 70.00 785.00 x 600.00)
+  (visible rect 0.00, 20.00 785.00 x 600.00)
+  (coverage rect 0.00, 20.00 785.00 x 600.00)
   (intersects coverage rect 1)
   (contentsScale 1.00)
   (children 1
     (GraphicsLayer
       (bounds 785.00 2266.00)
       (contentsOpaque 1)
-      (visible rect 0.00, 70.00 785.00 x 600.00)
+      (visible rect 0.00, 20.00 785.00 x 600.00)
       (coverage rect 0.00, 0.00 785.00 x 1800.00)
       (intersects coverage rect 1)
       (contentsScale 1.00)

[Matt Lewis]

I was able to reproduce on Sierra Release WK2 with:

run-webkit-tests tiled-drawing/scrolling/fast-scroll-iframe-latched-mainframe-with-handler.html  --iterations=500 --no-retry-failure -f -g

[Ryan Haddad]

The test seems to only be flaky on macOS Debug WK2 right now. Marked as flaky in https://trac.webkit.org/changeset/221270/webkit

[Radar WebKit Bug Importer]

<rdar://problem/42793016>