I think the fix for crbug/865978 may have taken care of this.

Indeed it has. I am still seeing that stretching artefact when opening a new incognito tab from the long-press menu and from the overflow menu though. Should we file another bug for these two entry points?

Actually, the stretching/distortion from "new Incognito tab" in the pop-up menu or the tools menu in the toolbar is all this bug ever was, so my comment in #6 is incorrect.

I'm running 70.0.3509.0 canary and also see a stretched Incognito NTP page that snaps down to correct proportions (just like screen recording at 0:02 in original report).

Should the status of this bug be marked as "Started"?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e96d2112071895c98375d959a87626d858cd5fc5

commit e96d2112071895c98375d959a87626d858cd5fc5
Author: Mark Cogan <marq@google.com>
Date: Fri Aug 03 06:18:59 2018

[iOS] fix NTP size in animation

This CL fixes the size distortion of the incognito NTP in the new tab animation.

The foreground animation view was assuming that the content view it animated had the same bounds as itself; this isn't correct for the incognito NTP, which is shorter to accommodate the toolbar. This CL instead repositions the content view correctly without resizing it. It also makes the animation view shorter (by StatusBarHeight()) to make this calculation cleaner.

Bug:  868292 
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Id49a3de2f3f62c246356da082f74285014a7b37a
Reviewed-on: https://chromium-review.googlesource.com/1160843
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580459}
[modify] https://crrev.com/e96d2112071895c98375d959a87626d858cd5fc5/ios/chrome/browser/ui/browser_view_controller.mm
[modify] https://crrev.com/e96d2112071895c98375d959a87626d858cd5fc5/ios/chrome/browser/ui/tabs/foreground_tab_animation_view.mm

Verified on canary 70.0.3515.0

This bug requires manual review: Less than 24 days to go before AppStore submit on M69
Please contact the milestone owner if you have questions.
Owners: amineer@(Android), kariahda@(iOS), cindyb@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

 Issue 871413  has been merged into this issue.

 Issue 866908  has been merged into this issue.

Verified on iPhone X iOS 11.4 on 70.0.3515.0 Canary

Approved.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b8d74f83f090d26bfaeeb255db185642e8285076

commit b8d74f83f090d26bfaeeb255db185642e8285076
Author: Mark Cogan <marq@google.com>
Date: Wed Aug 08 22:56:24 2018

[iOS] fix NTP size in animation

This CL fixes the size distortion of the incognito NTP in the new tab animation.

The foreground animation view was assuming that the content view it animated had the same bounds as itself; this isn't correct for the incognito NTP, which is shorter to accommodate the toolbar. This CL instead repositions the content view correctly without resizing it. It also makes the animation view shorter (by StatusBarHeight()) to make this calculation cleaner.

Bug:  868292 
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Id49a3de2f3f62c246356da082f74285014a7b37a
Reviewed-on: https://chromium-review.googlesource.com/1160843
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#580459}(cherry picked from commit e96d2112071895c98375d959a87626d858cd5fc5)
Reviewed-on: https://chromium-review.googlesource.com/1168322
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/branch-heads/3497@{#513}
Cr-Branched-From: 271eaf50594eb818c9295dc78d364aea18c82ea8-refs/heads/master@{#576753}
[modify] https://crrev.com/b8d74f83f090d26bfaeeb255db185642e8285076/ios/chrome/browser/ui/browser_view_controller.mm
[modify] https://crrev.com/b8d74f83f090d26bfaeeb255db185642e8285076/ios/chrome/browser/ui/tabs/foreground_tab_animation_view.mm