Chrome Version: Google Chrome 70.0.3538.76
Chrome OS Version: unknown
Chrome OS Platform: HP J4C98AA#ACJ
Network info: unknown

Please specify Cr-* of the system to which this bug/feature applies (add
the label below).

Steps To Reproduce:
(1) Enable device emulation via chrome.debugger.sendCommand and "Emulation.setDeviceMetricsOverride"
(2) Record video of tab via chrome.tabCapture.capture
(3) Observe that the dimensions of the video are not consistent throughout the video, even when the Chrome window is not resized

Expected Result: the dimensions of the video remain constant

Actual Result: the dimensions of the video vary between device-specific and desktop-specific over time, as the user interacts with the page.

From previous discussion with Chrome team members, we believe chrome.debugger doesn't maintain the dimensions of the tab content view across layout change events (e.g. loading a page, switching back from another tab, etc.). I.e., the tab content view is initially properly cropped to mobile dimensions, but then changes back to "desktop Chrome" dimensions. (These changes are bidirectional in general.) We were able to reproduce this behavior without using the chrome.tabCapture API, so it appears this is only caused by chrome.debugger.

How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?) 30% of time

What is the impact to the user, and is there a workaround? If so, what is
it? The impact is that it is impossible to create videos of experiences on emulated devices. There is no known workaround.

Please provide any additional information below. Attach a screen shot or
log if possible.

For graphics-related bugs, please copy/paste the contents of the about:gpu
page at the end of this report.