Previously, any time a text run was encountered that was outside the
detected opaque backdrop of a picture cache, all subpixel AA would
get disabled for that surface.
Recently, we added support for conditional subpixel mode, where a
list of excluded rects can be provided (compositor surfaces) that
require a text run to disable subpixel AA.
This patch extends that, adding an inclusion rect to the conditional
subpixel mode. This allows subpixel AA to be enabled on any text
runs that are within the bounds of the detected opaque backdrop
for a picture cache.
Differential Revision: https://phabricator.services.mozilla.com/D75027
99ed67fccb