UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.113 Safari/537.36

Steps to reproduce the problem:
Hi,
we are running Chrome inside docker using one of official selenium images:
docker run -d -p 4444:4444 selenium/standalone-chrome:latest
They are using Xvfb to run Chrome.

We have a test which opens chrome://webrtc-internals page and clicks on "Enable event log recording" and then make a WebRTC call from another tab.

Clicking on "Enable event log recording" should trigger Save As dialog (which we used to close via sending a return keycode to main Chrome window).

What is the expected behavior?
Save As dialog is opened and event log files can be found in Downloads directory

What went wrong?
Looks like dialog is not opened at all - there are no event log files

Did this work before? Yes Everything worked in Chrome 49

Chrome version: 53.0.2785.101  Channel: stable
OS Version: Ubuntu 16.04 on Linux 4.1.19-boot2docker
Flash Version: Not sure

Interesting that it works when I run the same test in selenium debug image:
docker run -d -p 4444:4444 selenium/standalone-chrome-debug:latest

The only difference between debug and non-debug images is that the first has built-in VNC server and window manager (fluxbox)