The windows canary (30.0.1567.1) of today is Aura.
Aura is the (not so) new UI stack that we use in Chrome OS. It does not use native widgets for controls and it fully uses the GPU when available. Compared with the traditional UI stack as seen in Chrome 28 or 29, the only native element is the top level window. Everything else is drawn by Chrome, composited by the the Chrome Compositor and uses Angle/GPU to present to the screen. Focus/Activation and in general input ins managed differently as well.
We've been working on the port to Windows for a long while and it is getting to the point where we can unleash it to the experimental channels. If you develop UI features outside the web contents area it is highly recommended you test your feature with an Aura build.
Most likely tomorrow's canary will be non-Aura, so today's canary is worth checking. Please file bugs using the regular procedure (crbug.com) based on the chrome version we can properly bucket it.
I don't have a good timeline for when Aura becomes the default, but it will. In short, when the metrics are good enough. For example stability, performance, latency, etc.
-cpu
Q&A
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Q:Why are we doing this?
A:Because we want to unify the UI stack across platforms. The end result is that Windows, Linux and Chrome OS will use the same UI stack while today each have a different one. Along the way we gain much flexibility to do fluid UI animations; the kind you can see today in Chrome OS shell.
Q:So Linux will be Aura too?
A:Yes. It is a bit behind Windows, but that is the plan. Volunteers/patches welcome. Note that there are no plans for the other platforms to use Aura.
Q:So if I only care about Blink/Webkit this does not concern me?
A:Not exactly. Aura forces compositing so be sure to test with --force-compositing-mode or use Aura.
Q:I have my own build, what switch to I give chrome to try it?
A:There is no switch, it is a compile-time define. In the gyp defines specify use_aura=1 then rebuild the project files then rebuild the targets.
Q:How do I tell a given Chrome build is Aura?
A:The last part of the version is .1, also the page at chrome://version tells you if it is Aura, for example canary is "30.0.1567.1 (Official Build 211921) canary Aura."
Q:What if my computer does not have a GPU?
A:We have now a pure-software fallback. So it should just work. Check chrome://gpu for the status of GPU acceleration.
Q:I tried but I am getting BSODs (blue screens), what gives?
A:Please file a bug with the information in chrome://gpu. Then update your video drivers.
Q:How about testing coverage?
A:We do have trybots and Aura testers in the waterfall, but the coverage is not to the level we want yet. We are investigating options to get more coverage.