Hardware accelerated H.264 decoding landed in Firefox on Windows Vista and later

I have been hard at work getting our H.264 support on Windows Vista and later hardware accelerated using DXVA2. I'm happy to say that this finally landed in Firefox 23 Nightly builds. With this patch we'll use the GPU to accelerate H.264 video decoding when possible on Windows, which greatly reduces our CPU and power usage.

If you spot a bug in H.264 video in Firefox Nightly builds, please file a bug in Core: Audio/Video. Bonus points if you toggle the pref "media.windows-media-foundation.use-dxva" to false, reload the video, and tell me whether the bug still happens!

Notes:

1. H.264/AAC/MP3 support on Windows 7 and later is shipping in Release builds in Firefox 21 next week, Vista gets it in Firefox 22.
2. Edwin Flores is working on our H.264/AAC/MP3 support on Mac and Linux.
3. I'm currently working on getting MP3 support for Windows XP using DirectShow, it will probably land next cycle (Firefox 24).