(1) Reduce size of content tiles from 2048 x 512 to 1024 x 512.
This reduces the large extra overhead of tiles on screens that
are not 4k resolution.
(2) Remove small 128 x 128 tiles.
These typically create a lot of OS compositor surfaces, which
adds significant overhead on some platforms. Having them be
normal content tiles also means no resizing of the picture
cache for the UI when the awesome bar and/or status bar is on.
(3) Add support for very narrow cache surfaces.
This is a special use case for scrollbar caches. It's worth
supporting this special case for the significant memory and
performance savings for these surfaces.
Differential Revision: https://phabricator.services.mozilla.com/D51541
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extra : moz-landing-system : lando
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