But today I checked latest version of Google Chrome and find that situation is completely changed.
From Stage3D now disabled in plugin, but only disabled in Google Chrome configuration by default.
There is screenshot of Unreal Engine 3 flash demo: 1920x1200 screenshot
My configuration is: Ubuntu 12.04 32-bit, AMD HD6950 1GB, FGLRX driver, Google Chrome 21.0.1180.81 with flash player 220.127.116.11.
Install latest Google Chrome
Run it with "--ignore-gpu-blacklist" flag
Open chrome://gpu-internals/ and check Stage3D status
Which version of Google Chrome and flash plugin do you have? What's about hardware?
You need to note that Chromium hasn't required version of flash plugin, it's use 11.2 version which doesn't support hardware acceleration on Linux.