UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36

Steps to reproduce the problem:
1. construct a valid Facebook's oauth url like https://www.facebook.com/v3.1/dialog/oauth/?client_id=.......
2. initiate chrome.identity.launchwebAuthFlow with that url
3. log in
4. initiate chrome.identity.launchwebAuthFlow with that url, so Facebook doesn't ask for a username any more, only for a  password
5. Continue button is aligned to the bottom, but is not visible in the oauth popup

What is the expected behavior?
Continue button should be visible. When you enter the url you constructed in step 1. into a normal chrome window (not through launchwebAuthFlow), it displays ok. 

What went wrong?
Footer has 28pxs outflowing, coincidentally the popup window's header is also exactly 28pxs high. Footer is 28px outflowing because it's positioned 'position:absolute' and 'bottom:0' to the body. Which means that the body itself is 28px higher than it should be. 

My assumption is that the document.height might be miscalucated in this special popup launched by chrome.identity.launchWebAuthFlow

WebStore page: 

Did this work before? N/A 

Chrome version: 68.0.3440.106  Channel: n/a
OS Version: OS X 10.13.6
Flash Version: 

Version 68.0.3440.106 (Official Build) (64-bit) 
and 
Version 71.0.3555.0 (Official Build) canary (64-bit)

both has this issue.
both have this.
 

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