Version: 51?
OS: All

This bug will be valid once https://codereview.chromium.org/1819073004/ lands. Here now so I can refer to it inside a source-code comment.

What steps will reproduce the problem?
(1)Load the attached file

What is the expected output?
- what Firefox does

What do you see instead?
- Misaligned <tr> backgrounds.

There are 2 bugs here. All can be fixed by fiddling with TableCellPainter::paintParentBackgroundsBehindCell

When background-image-size is 100%, and cell has (rowspan || colspan) > 1, image in the background cell will be too wide/tall. The reason is that we are using union of cell rect and background rect to draw backgrond image, instead of using background rect to size the background image, and cell rect for drawing.

For this bug to be fixed, we need to extend BoxPainter functionality, so that paintFillLayer can use separate rectangles for image positioning and image painting.

The other bug is that background image origin is incorrect in vertical painting modes for rowspan/colspan cells. background origin should be the topleft corner of parent element (colgroup, etc), not the topleft corner of union of cell rect and background rect.

Workaround: specify image background width in units that are not a percentage.
Both bugs happen in the attached file.
 

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