Use the color clip corresponding to the last background-image instead
of the last background-clip. (There may be more clips than images and
clips are repeated if there are less clips than images.)
Add a test.
Move DL items from gfx to layout and implement corner clipping
Implement corner clipping.
Remove PixelFormat from WebrenderImageInfo.
Use WebRender text shadow.
Remove MallocSizeOf and Deserialize for DL items.
Closes#19649, closes#19680, closes#19802
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Implement corner clipping.
Remove PixelFormat from WebrenderImageInfo.
Use WebRender text shadow.
Remove MallocSizeOf and Deserialize for DL items.
Closes#19649, #19680, #19802
