Merge branch 'chromium-update-with-gn'

This brings in the new stable version 54 which also introduces a lot of
security fixes:

  CVE-2016-5198: Out of bounds memory access in V8
  CVE-2016-5181: Universal XSS in Blink
  CVE-2016-5182: Heap overflow in Blink
  CVE-2016-5183: Use after free in PDFium
  CVE-2016-5184: Use after free in PDFium
  CVE-2016-5185: Use after free in Blink
  CVE-2016-5187: URL spoofing
  CVE-2016-5188: UI spoofing
  CVE-2016-5192: Cross-origin bypass in Blink
  CVE-2016-5189: URL spoofing
  CVE-2016-5186: Out of bounds read in DevTools
  CVE-2016-5191: Universal XSS in Bookmarks
  CVE-2016-5190: Use after free in Internals
  CVE-2016-5193: Scheme bypass

Detailed announcements about these changes can be found here (latest to
oldest):

https://googlechromereleases.blogspot.de/2016/11/stable-channel-update-for-desktop.html
https://googlechromereleases.blogspot.de/2016/10/stable-channel-update-for-desktop_20.html
https://googlechromereleases.blogspot.de/2016/10/stable-channel-update-for-desktop.html

The update process of Chromium has been a bit bumpy on our side, because
version 54 also did the switch from GYP to GN so it wasn't just a matter
of updating the upstream-info file.

I've tested the Flash plugin (which runs fine) and WideVine manually,
although I couldn't get WideVine to work (I was running this within a VM
though).

So if people want to use WideVine they need to use Chrome instead until
we got this sorted out.

VM test results along with builds for all platforms can be found here:

https://headcounter.org/hydra/eval/339328

I'm going to backport these changes to stable as soon as the
tests/builds succeed there as well.

Closes: #19565
Closes: #20120