commit 04bb7a49838efbe8134ffa2f590e15fb00630849
author Michael Lippautz <mlippautz@chromium.org> Thu Dec 14 19:41:19 2023
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Thu Dec 14 19:41:19 2023
tree 18d434da02a8c0ae00ab8d47827a4ebc6358d1f6
parent 7336c8948d33d9ef8dae7aeb7f06dd0b2b55c268

DOMWindow: Set wrapper reference to global proxy object

The JS global proxy object already points to the
{Local,Remote}DOMWindow via internal field. Make
DOMWindow::main_world_wrapper_ point to the global proxy object as
well. Avoid using the already existing AssociateWithWrapper() methods
as they require that a context is properly set up.

{Local,Remote}WindowProxy's global_proxy_ field becomes a regular
traced reference without setting up the class id.  The GC treats it
the same way for liveness but heap snapshot generation would not
consider it as a candidate to merge nodes with a JS object as it's not
ScriptWrappable's::main_world_wrapper_.

This way Wrappable/Wrapper pairs (represented by ScriptWrappable/V8
objects) are properly set up in the entire codebase and may on a
high-level considered as one object or "entity".  This allows heap
snapshot generation to merge the nodes without considering the class
id state on the reference. Ultimately, this allows us to get rid of
the class id eventually and speed up all TracedReference creation.

Delete WPT test:
performance-timeline/tentative/performance-entry-source-deleted-frame.html

Rationale:
- The test was added to check that a PerformanceEntry does not leak
  Window objects via its source property when PerformanceEntry objects
  are stashed away to be consumed later.
- The test merely checks that we return a null Window for a detached
  Window. This is not what it was added for.
- The test fails for FF and Safari [1]
- Writing this test properly is really hard: The JS wrapper is already
  materialized in the iframe via `performance.mark()`. Thus accessing
  `childEntry` from the main frame leaks the other iframe via the JS
  wrapper constructor (that points to its context). In order to avoid
  this, one must stash the Window itself in a weak ref, perform GC at
  the event loop, and then check the weakref. Performing GC at the
  event loop is not supported in WPT as of today.

[1] https://wpt.fyi/results/performance-timeline/tentative?label=master&label=experimental&aligned&q=performance-timeline%2Ftentative%2Fperformance-entry-source-deleted-frame.html

Tests: DevTools frontend e2e memory/*
Bug: chromium:1218404
Change-Id: I4e3273c6ca7da8e3241b4f9ac78c76932c52bce2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2953842
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1237676}