When the computed restyle damage is empty, do not do a layout. Instead,
just rebuild the display list. In the future, even that can be omitted,
but that requires changes to the compositor.
These kind of relayouts commonly happen when the cursor is moving around
the page and no style rules cause changes to :hover.
Testing: This is covered existing WPT tests and should only have
performance
impacts. Unfortunately there are currently no performance tests.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
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