Tried testing the issue on reported chrome version #69.0.3497.72 using Ubuntu 17.10,by following below steps.

Steps:
=====
1.Launched chrome.
2.Navigated to google.com.
3.Opened dev tools and selected device toolbar (Mobile emulation),observed that the screen can be resized to 370px width.

Attached screencast for reference.
@Reporter: Could you please review the attached screencast and let us know if anything is being missed from our end.

Thanks.!

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I meant without having to open up F12 tools and finding that device test option.
You can't just resize the main window to be a standard phone width.

Thank you for providing more feedback. Adding the requester to the cc list.

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

Tried testing the issue as per comment#3 on reported chrome version using Ubuntu 17.10 by following below steps.

Steps:
=====
1.Launched chrome.
2.Quickly resized window , observed that the size of the window of chrome version #69.0.3497.72 after resizing is larger than the screen on chrome version #68.0.3440.106.

Attached screencast for refrence.
@reporter: Could please review the screencast and help us in confirming the issue. If possible request you provide screencast of the issue, so that it would be really helpful for better triaging of the issue.

Thanks.!

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That's it, very wide minimal window size which could be problematic for testing or for netbook devices.

Thank you for providing more feedback. Adding the requester to the cc list.

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

Tried testing the issue on chrome version #68.0.340.106 and reported chrome version #69.0.3497.72 on Ubuntu 17.10 as per comment#3.
Observed that the resized window of chrome version #68.0.3440.106 is now not same as the mobile screen, but lesser size compared to chrome version #69.0.3497.72. As the issue is not getting reproduced at TE end, hence removing Needs-Bisect label.

Attached screencast for reference. Requesting anyone from UI team to look into the issue.
Thanks.!

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 Issue 881103  has been merged into this issue.

I received a comment on #889922 (https://bugs.chromium.org/p/chromium/issues/detail?id=889922#c6) mentioning that the minimum size has been increased recently and that it's expected.

What am I missing?

The increase in minimum window width in M69 is by design. Please see  issue #849784 .

If the change in minimum width is by design, one can only resort to using mobile emulation to change the window size below the minimum width. Howevery, sadly, there is a known bug around clicking element: https://bugs.chromium.org/p/chromedriver/issues/detail?id=2144

This makes it impossible to test on mobile viewports if I upgrade to chrome v69.

As per comment#8 the issue is not getting reproduced at TE-end, hence adding TE-NeedsTriageHelp label and requesting someone from appropriate team help in providing further inputs on this issue.

Thanks!

**UI mass Triage**

As per c#11, closing the issue.If you feel this issue should still be addressed, feel free to reopen it or to file a new issue.

Thanks!