Tested the issue in Android and able to reproduce the issue. 

Steps Followed:
1. Launch Chrome in landscape mode.
2. Navigate to any URL - https://lib.beebuzziness.com/media/b3e10ff0-30d8-11e7-b450-dfde136e0883/ 
3. Swipe up the screen once to open next page.
4. Tap on ‘+’ button.
5. Switch to “Comfort Mode” to open in full screen mode.
6. Observed that a white bar is displayed in the bottom of the screen.

Chrome versions tested:
65.0.3325.109(Stable), 66.0.3393.2(Dev), 67.0.3396.3(Canary)

OS:
Android 8.1.0

Android Devices:
Pixel 2 XL

Using the per-revision bisect providing the bisect results,
Good Build - 65.0.3299.0 (524906)
Bad Build - 65.0.3300.0 (525555)

You are looking for a change made after 525500(GOOD), but before 525501(BAD).

CHANGELOG URL:
The script might not always return single CL as suspect as some perf builds might get missing due to failure.
https://chromium.googlesource.com/chromium/src/+/e0c27aa594d4584e9dff30a0b6e3604089ad9a0c

@dtapuska:  Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to owner concerned.

Please navigate to below link for log's and video--
go/chrome-androidlogs/833440

Note: 
1. This issue is not observed in Desktop.
2. This issue is not observed in FireFox mobile version.

Thanks!

Hello,

How is it possible to know the evolution of a fix for this issue ?

Thank you

Hi,

The document.documentElement.clientWidth/Height aren't affected. Might not be much, but that's what I used as a workaround while this is still an issue.

Hope this can help someone...

Fixed in Chrome 69.

I think I'm having exactly the same issue on Chrome for iPhone.
Using version 68 at the moment. I do not think version 69 is available yet as I don't see any update on the AppStore. 

Is this also fixing the issue for iOS on the future version 69? 

No unfortunately the fix is inside Blink (the web platform engine used in Chrome on everything other than iOS). Chrome on iOS uses the webkit engine from Apple. You'll need to file a bug there. bugs.webkit.org as I presume the same issue happens for Safari on iOS as well.