I'm baffled why those two separate issues are treated as the same.
The bug report for chromium mentions that the "flashing" from fullscreen to normal mode is fixed (which is not true, at least here it isn't...) and that the remaining issue is with the size.
Well, if I play a flash video, even if I get it to stay fullscreen for a few seconds (after rapid gunfire clicking), it still goes back to normal. And yes, that's independent of mouse and/or keyboard events/keypresses.
This happens for me under Gnome-shell, not Unity(3D) where it behaves as expected.
user@terminal:~$ uname -a
Linux Obsidian 3.2.0-30-generic #48-Ubuntu SMP Fri Aug 24 16:52:48 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
user@terminal:~$ chromium-browser --version
Chromium 18.0.1025.168 Ubuntu 12.04
user@terminal:~$ lspci|grep Graphics
00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)
00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)