commit 362b9e1aefdc1846862db8fb097d87ae2ab19992
author Emil A Eklund <eae@chromium.org> Thu Nov 29 22:20:45 2018
committer Commit Bot <commit-bot@chromium.org> Thu Nov 29 22:20:45 2018
tree a26f787a67eb1ab6afadbe66648501e4c42cf97c
parent 96ea470027c441ada9b8ff14372f7e422650afc8

[LayoutNG] Fix O(N^2) in NGInlineNode::ShapeText

When shaping the content of an inline node in NGInlineNode::ShapeText we
assume that the number of runs is small and iterate over all of the runs
for each inline item. This assumption holds true for most content, there
are certain cases where the assumption is incorrect however, such as the
euckr-decode-ksc_5601.html WPT test where each CJK glyph is wrapped in a
span and separated by space characters of a different glyph. This causes
each of the 10k+ items to iterate over 10+ runs which is very expensive.

This patch adds an optional context argument to ShapeResult::SubRange so
that context (the relevant run) may be maintained across invocations and
thereby avoids an extra loop over all of the runs for each SubRange call.

Change-Id: I2ee610a60e33fe4389277fc275a9b8d670453a31
Reviewed-on: https://chromium-review.googlesource.com/c/1354561
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612403}