Only on
- iPhone X iOS 11.4
- iPhone X iOS 12.1

Suspecting ios-related CLs:
https://chromium-review.googlesource.com/c/chromium/src/+/1355179
https://chromium-review.googlesource.com/c/chromium/src/+/1352958
https://chromium-review.googlesource.com/c/chromium/src/+/1354414
https://chromium-review.googlesource.com/c/chromium/src/+/1354329

Adding authors as CC; any idea?

I'm bisecting culprit. Will update the bug soon.

Justin, it looks like b2432bbba3c089f0f4c117d6a7e57914a49249fb is a culprit.

Thanks, Eugene!

Can/should we revert the culprit CL?
(Deferring to APAC sheriffs)

I'm investigating!

Any updates? ios-slimnav still fails.

Fix here: crrev.com/c/1356034

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/51a04f82f31aa29ebbb2d3c3e8de6c350dac6179

commit 51a04f82f31aa29ebbb2d3c3e8de6c350dac6179
Author: Justin Cohen <justincohen@google.com>
Date: Fri Nov 30 05:14:59 2018

[ios] Center long press WKebView links for egtests.

EarlGrey doesn't natively support tapping on links within WKWebView, and the
long press implementation hack used doesn't work well with links near the edge
of the page when allowsBackForwardNavigationGestures is enabled.  As this is a
test only issue, a simple fix is to just center the items being long pressed.

Tbr: eugenebut
Bug:  910375 
Change-Id: Ibb7079b22e1ce1d8baa52f0205be038dfec9d2c4
Reviewed-on: https://chromium-review.googlesource.com/c/1356034
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612571}
[modify] https://crrev.com/51a04f82f31aa29ebbb2d3c3e8de6c350dac6179/ios/chrome/browser/context_menu/context_menu_egtest.mm
[modify] https://crrev.com/51a04f82f31aa29ebbb2d3c3e8de6c350dac6179/ios/testing/data/http_server_files/links.html

The bot is green as of https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/ios-slimnav/477. Thanks for the fix.