commit a5dd044bb95332f67c5b12b6d1b97e4e6816f67c
author Benoit Lize <lizeb@chromium.org> Wed Feb 07 12:49:16 2024
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Wed Feb 07 12:49:16 2024
tree 4d764f6c6ffce5cabe6a88a38a9cd3ca3f33fba2
parent c9bbbf941f955819d2c667218658699deaaa784c

[cc] Allow reclaim of <canvas> resources outside the viewport

With canvas hibernation (enabled on most platforms), when a 2D canvas is
part of a background page, its backing TextureLayer is cleared, allowing
GPU-side memory to be freed. Unfortunately, this doesn't work, since
there is a reference to the previous texture held in the active tree,
impl-side.

A recent change
(https://chromium-review.googlesource.com/c/chromium/src/+/5063730)
allows these resources to be freed when compositor frame eviction
happens, i.e. when viz returns the resources. However, as noted in
crbug.com/1516888, this does not apply to resources that haven't been
imported into viz. This means that all <canvas> elements that are not in
the viewport at the time where the page gets backgrounded are not
evicted by this path, or any other (it makes sense, since theh CL above
relies on viz returning resources, and it cannot return a resource it
doesn't know about).

This CL addresses the case of these canvases. It was observed to happen
on google docs for instance, which uses 2D canvas for its rendering, but
should apply more broadly (e.g. with canvas-based ads that are outside
the viewport). Potential savings on high resolution screens are >10MiB
per google docs tab (and similar sites).

Bug: 1516888
Change-Id: Id6a4d289565119693999dda778b743b3e78cce11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5176918
Commit-Queue: Benoit Lize <lizeb@chromium.org>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1257294}