tree 3930cd92e002d7866c39b2703df66a38d1c45e39
parent ec8eecd43e984630a8a15195a2dd58c987462f80
author Kevin McNee <mcnee@chromium.org> 1706145051 +0000
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> 1706145051 +0000

Reduce memory usage of NavigationPredictor AnchorElementData

NavigationPredictor stores a map of information about anchor elements
which can grow quite large, especially for long lived pages with many
anchors.

The following fields are not used and are now removed:
ratio_visible_area, ratio_distance_center_to_visible_top,
ratio_distance_root_bottom.

We change AnchorElementData to no longer store the
blink::mojom::AnchorElementMetrics sent by the renderer, but have fields
to only store the required information. Fields that do not need to be
stored are omitted. Some fields can use a smaller type to store the
necessary information (e.g. the font size is bucketed, and only needs 1
byte to represent possible values). bools are packed together with bit
fields. Fields are arranged to reduce the padding needed for alignment.

Using base::trace_event::EstimateMemoryUsage, the memory usage for the
youtube home page was 56,480 bytes. With this change, it's reduced to
44,960 bytes.

Bug: 1506262, 1419556
Change-Id: Ie430df1626b44ef80af6715f35d91b5f807f24d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5234754
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Simon Pelchat <spelchat@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1251839}