[customize-titlebar] Expose gfxInfo's results to 'Graphics Toolkit' variable

[xabolcs]

Currently NTT 3.3 doesn't care too much to detect the Graphics Toolkit:

    ....
    toolkit: "cairo",
    ...

In the mean time Azure introduced, the successor of Cairo.
A trivial fix would be to change "cairo" to "azure" and close this issue. :)

But Azure has / would have a lot of backend.
So instead of a pure "azure" IMHO it would be more nicer to have an "azure (backendname)"-like output, e.g. "azure (cairo)" or "azure (skia)".

The code below exposes which Azure backend is used.

const { classes: Cc, interfaces: Ci, utils: Cu } = Components;
var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo); gfxInfo.getInfo().toSource();

Please note that gfxInfo.getInfo changed it's output in Gecko16 → 17: from ({AzureBackend:"aaa"}) it changed to ({AzureCanvasBackend:"aaa", AzureFallbackCanvasBackend:"bbb", AzureContentBackend:"ccc"})!

@firefoxnightly tweeted that in this case AzureCanvasBackend should be used. :)