The test has started timing out on Windows without an obvious culprit.

https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7%20(dbg)

First failing build:
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7%20%28dbg%29/builds/7940

Error messages:

10:28:07.601 628 [36247/42308] paint/invalidation/compositing/should-not-clip-composited-overflow-scrolling-layer.html failed unexpectedly (test timed out)

Regressions: Unexpected timeouts (2)
  paint/invalidation/compositing/should-not-clip-composited-overflow-scrolling-layer.html [ Timeout ]
  paint/invalidation/compositing/should-not-clip-composited-viewport-scrolling-layer.html [ Timeout ]

Tried reverting http://crrev.com/2458253002, but that did not help. Relanded the original CL.

Could also be caused by http://crrev.com/2469433003, but unlikely. That patch has been reverted before for a different issue, but eventually ended up being innocent.

Please investigate.