[leshchenko1979]

Fixes #28.

Problem

display: table was parsed and stored but had no consumer anywhere in layout/: the display enum had no table/table-row/table-cell values, ParseDisplay defaulted everything to block, tagDefaults had no UA defaults for table/tr/td/th, and there was zero table code. Every cell was laid out as a block child, so a three-column table stacked its cells vertically.

Measured against Chromium on a 21-case harness (% of pixels differing by more than 32 per channel):

case	before	after
08-table	5.15 %	0.09 %
18-table-tr-row2	8.10 %	0.13 %
17-table-div	1.20 %	1.20 % (uses flex, unaffected)

What this adds

Four display values (table, table-row, table-row-group, table-cell) with their UA defaults for table/thead/tbody/tfoot/tr/td/th (th also font-weight: 700), plus a table layout pass in layout/table.go:

• columns — an explicit cell width is that column's preferred width; a column without one takes its cells' max-content width; the total is scaled down proportionally when it overflows the table, and the slack is shared equally when it does not. That is what a browser's auto table layout converges to for the markup people actually write.
• rows — stacked vertically, each as tall as its tallest cell.
• row groups — thead/tbody/tfoot are transparent for layout.
• height — a table's height is the sum of its rows, never the definite height the flex pass hands down. In CSS a table never stretches, and adopting that height pushed every sibling below it out of place.
• cell offsets — relative to the row. Storing the absolute y on both the row and the cell made the renderer add the row offset twice, so every row after the first landed one row-height too low.
• main axis — rows are mapped to a horizontal main axis so the intrinsic-size estimator maxes its cells instead of summing them; otherwise an auto-height wrapper around a table came out twice as tall as the table.

Tests

layout/table_test.go, 7 tests: cells side by side, auto columns sharing the slack, rows stacking and sizing to the tallest cell, the table ignoring a definite container height, an explicit height still winning, row groups being transparent, and display: none cells not consuming a column. Two of them (cell-offset relativity and the auto-height wrapper) were verified to fail on the pre-fix code.

go test ./... and go vet ./... pass. Existing golden SVGs are unchanged.

Not implemented

table-layout: fixed, border-collapse, rowspan, colspan. The cases above need none of them, and guessing at border-collapse would change the geometry of every bordered table.