Layout Team & Project Warden Status - June 1, 2015

[Emil A Eklund]

The layout team is a long-term team that owns the layout code in blink.
The current focus is primarily on code-health (building on Project
Warden) and layout performance.
See https://sites.google.com/a/chromium.org/dev/blink/layout-team for
more information.

Warden is a project to cleanup and fix long standing issues in order
to increase developer productivity.
See goo.gl/VEv1YQ for more information.

Updates since last meeting (on Tuesday, May 25th):

Performance Tracking (benjhayden)
- Continuing to focus on trace viewer overall rather than limited to
layout performance.
- Visualizing layout in trace viwer.
- Interaction records.

Scrolling (skobes) [crbug.com/417782]
- Figured out a way to run the WebFrameTest unit tests with booth root
level scrolling turned on and off. Going through tests to catch
regressions.
- Learned more about page scale factor, turns out that the initial scale
factor cause the FrameView to be a different size.

Line Boxes (szager) [crbug.com/321237]
- Landed over the weekend, re-baselines almost done. Yay!

Flexbox (cbiesinger) [crbug.com/426898]
- Updated min-size handling to match latest version of spec.
- Sycned up with Microsoft and Mozilla about their flexbox plans to
ensure compatibility across browsers.

Menu list refactoring (dsinclair) [crbug.com/370462]
- Done!

Fullscreen (dsinclair) [crbug.com/370459]
- Landed fix to persist plugins over re-attach. Subsequently reverted
due to browser_test failures. Looking into failures and plan to
re-land this week.

Misc Warden (dsinclair, pilgrim)
- Containing work to slim-dopwn LayoutObject. (pilgrim)

Region-based multi-column support (mstensho) [crbug.com/334335]
- Will start to delete the old multicol code this week. It's no longer
possible to enable it and no major regressions have been found.

Text
- Continuing work on complex text performance. (eae)
- Experimenting with only inheriting inheritable properties into text
nodes, not yet convinced that it affects performance noticeably, but
it WILL increase memory usage, since we create a new ComputedStyle
object for each text node (instead of sharing with the parent).
Each text node that has the same parent could easily share the same
ComputedStyle object, though, but we'd still be going to increase
memory usage. (mstensho)
- Fixed justification crash issue. (kojii)
- Investigating orthogonal writing modes issues. (kojii)
- Unicode variation selectors support in progress. (kojii)

Importing Test Suites
- Working on importing CSS Writing Modes test suites. (kojii)
- Imported HTML tests. (tkent)

Removing DeprecatedPaintLayer [crbug.com/260898] (chadarmstrong)
- Started looking at moving hit testing from DeprecatedPaintLayer to
Box model object.
- jchaffraix helping chadarmstrong get up to speed.

Add API for layout [crbug.com/495288] (leviw)
- Meeting last where where the plans for the grand layout refactoring
was discussed. We agreed that the first step is to define (and over
time refine) an API for interacting with layout. Meeting notes at
https://www.chromium.org/blink/layout-team/meeting-notes/may-28-2015
- Wrote up a document outlining the plan, sent out to blink-dev.
https://docs.google.com/document/d/1qc5Ni-TfCyvTi6DWBQQ_S_MWJlViJ-ikMEr1FSL0hRc

Multipart images [crbug.com/308999] (japhet)
- Implemented support for multipart image documents.

Musc Performance
- Looked into SVG spinner performance and found layout bug where SVG
paths where regenerated unnecessarily. Fixing the bug should give us
at least a 50% perf improvement. (esprehn)

Logistics
- cbiesinger gardener Friday/Monday.