Chrome Version:51.0.2704.23 / 8172.9.0 dev 

What steps will reproduce the problem?
1) On the device, open few tabs and windows for desktop capturing
2) Download and install the desktopCapture extension from https://chromium.googlesource.com/chromium/src/+/master/chrome/common/extensions/docs/examples/api/desktopCapture
3) Launch the Desktop Capture extension 
4) Observe buttons 'Start', 'Cancel' and 'Start from background page' 
5) Now, try to resize the desktop capture window either horizontally or vertically ( do not minimize or maximize the window)

Expected result:
Desktop capture window should be scrollable and all the contents- windows and buttons should be visible even after reducing the size of the window

Actual result:
'Start', 'Cancel' and 'Start from background page' buttons are not visible and windows are visible partially after reducing the size of the window