Bug 1922856 [wpt PR 48482] - [line-clamp] Always clamp immediately af…

…ter a line box, a=testonly

Automatic update from web-platform-tests
[line-clamp] Always clamp immediately after a line box

In our initial implementation of `line-clamp: auto`, we allowed
clamping after lineless boxes, in order to better match the behavior
of `line-clamp` as it follows from the spec's `continue: discard`
model, even though our implementation uses a different model which is
not yet in the specification (see
w3c/csswg-drafts#7708).

However, in hallway conversations in TPAC 2024, we agreed that it
would be better for this model to instead only allow clamping
immediately after a line. If the first line does not fit, we calmp at
the first line even if that overflows the clamp height. If there are
no lines, we do not clamp. This patch implements this.

Additionally, a previous patch (https://crrev.com/c/5868971) had
increased the memory size of `LineClampData` from 8 to 20 bytes,
causing a memory regression. This patch shrinks it to 12 bytes, since
`LineClampData` no longer needs to keep track of how many block boxes
there are between the last line and the clmap point, and now OOFs
after the clamped line behave the same when clamping by a number of
lines or by a height, so there is no need for a flag to distinguish
these behaviors. This patch also adds a size assertion for
`LineClampData`.

This patch also changes or removes some WPT tests that were written
assuming the previous behavior.

Bug: 40336192, 368114054
Change-Id: I8c8afebb5dc566de92112cee2fcf24a2e60b42c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5904459
Reviewed-by: Ian Kilpatrick <ikilpatrickchromium.org>
Commit-Queue: Andreu Botella <abotellaigalia.com>
Cr-Commit-Position: refs/heads/main{#1364495}

--

wpt-commits: 1563c1e3a851d13982c2e9a0c2eabb8287823b35
wpt-pr: 48482

UltraBlame original commit: 5751601c841de1f7d26475e22ebaa4d8ca71b474

testing/web-platform/tests/css/css-overflow/line-clamp/line-clamp-auto-011.tentative.html

@@ -141,21 +141,11 @@
 0
 it
 should
-not
+still
 show
-any
-lines
-and
-its
-content
-box
-'
-s
-intrinsic
-size
-should
-be
-zero
+the
+first
+line
 "
 >
 <

testing/web-platform/tests/css/css-overflow/line-clamp/line-clamp-auto-025.tentative.html

@@ -26,7 +26,7 @@
 clamp
 point
 is
-visible
+hidden
 <
 /
 title
@@ -99,13 +99,13 @@
 "
 reference
 /
+webkit
+-
 line
 -
 clamp
 -
-auto
--
-025
+005
 -
 ref
 .
@@ -133,9 +133,10 @@
 :
 auto
 is
+at
 the
 last
-one
+line
 where
 the
 box
@@ -145,38 +146,27 @@
 t
 overflow
 .
-Since
-non
--
-inline
-abspos
-have
-a
-clamp
-point
-after
-them
-and
-they
-don
+An
+immediately
+following
+box
+even
+if
+it
 '
-t
-take
-up
-any
-space
-in
-the
-container
+s
 an
 abspos
-right
-at
-the
-boundary
+that
+takes
+up
+no
+block
+size
 should
+still
 be
-visible
+hidden
 .
 "
 >
@@ -205,6 +195,11 @@
 32px
 serif
 ;
+padding
+:
+0
+4px
+;
 background
 -
 color