Probably linked to the toolbar flag.

I'm pretty sure it's because we aren't repositioning the omnibox popup when moving from landscape to portrait.

I can reproduce if I type 'a' in the omnibox in landscape, and switch to portrait -- I get something that looks like this:
https://isolateserver.appspot.com/browse?namespace=default-gzip&digest=bd0c4c832d78e9d2b9747a92861d2a1ba978793c&as=ToolbarTestCase_testToolbarOmniboxTyping.png

(note the first result is obscured).

Lowering to RBS, although it's possible we won't put this fix in 63...

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b2e3ad14a8883fa0fe6b4da67aa2753860ae364e

commit b2e3ad14a8883fa0fe6b4da67aa2753860ae364e
Author: Justin Cohen <justincohen@google.com>
Date: Mon Nov 20 14:56:35 2017

Fix omnibox popup on iPhone X screen rotation.

Bug:  784841 , 786552
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I9469e3b2d69135ff7e39977ef0f50b7cb4ac72a4
Reviewed-on: https://chromium-review.googlesource.com/777585
Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517821}
[modify] https://crrev.com/b2e3ad14a8883fa0fe6b4da67aa2753860ae364e/ios/chrome/browser/ui/toolbar/web_toolbar_controller.mm

I can't reproduce this anymore, but the bots are still failing, will continue to investigate.

Looks like https://chromium-review.googlesource.com/783323 fixed the remaining error case.

[Auto-generated comment by a script] We noticed that this issue is targeted for M-63; it appears the fix may have landed after branch point, meaning a merge might be required. Please confirm if a merge is required here - if so add Merge-Request-63 label, otherwise remove Merge-TBD label. Thanks.

I don't think this fix meets the bar for M63, moving to 64 and removing Merge