If we switch the render mode from D2D to GDI at runtime, either due to user preference changes or issues such as driver crashes, we end up using DirectWrite fonts in GDI mode, which is an untested configuration. To stay in a standard, tested configuration when switching to GDI rendering, we should also switch the font back-end from DW to GDI. This will require rebuilding the system font list and discarding all font objects from the font cache, font-groups, etc. (See also comments in bug 606419.)

Nominating to block 2.0, because this blocks the suggested approach to resolving bug 564444.

Doesn't need to block since 564444 isn't blocking.

We don't need to support pref liveness in this case, and while it sort of sucks that a display driver crash can put us into an unsupported case, I also don't think drawing glitches like bug 564444 are bad enough to force us to do this. That being said, if this sort of thing causes worse bugs, we'll of course revisit this choice!