Fix absolute-flow's auto positioning
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If an absolute positioned flow has no top, bottom, left, right property, its hypothetical box position should be the margin-end of its previous sibling, not the border-end.
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- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#12676 (github issue number if applicable).
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- [x] There are tests for these changes
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Simplify the situations in which subpixels are accumulated, so that it
is only done for translation or identity transformation matrices. Also,
apply accumulated subpixels to more operations in PaintContext. This
fixes several pre-existing reftests and hopefully will eliminate
off-by-one errors in flaky reftests.
Fixes#10881.
Instead of simply rounding layer origins and discarding subpixel
offsets, accumulate them by transforming them into the space of the
next child stacking context. This is an attempt to eliminate subpixel
differences that are caused by different stacking context boundaries in
reference tests.
Currently these accumulated subpixels are only used for text
positioning, but the plan is that they can be used for all drawing in
the future.
Without this change, each text fragment in a block that establishes a
stacking context will establish its own stacking context. This is
unnecessary and increases the amount of work done during display list
construction.
* [fix] Input line height and styling
* [new] Input line height ref test
* [fix] Test for input in manifest
* Updated CSS tests with new expected failures.
