1597445 - Audit nsIDocShellTreeItem usage in mozilla::EventStateManager::WalkESMTreeToHandleAccessKey in dom/events/EventStateManager.cpp

Status: NEW

(Core :: DOM: Navigation, defect, P3)

Description

[Kannan Vijayan [:djvj]]

In file dom/events/EventStateManager.cpp

Code is already instrumented to handle remote processes.

But usage of DocShell tree instead of BrowsingContext tree remains.

Usage is mostly iterating recursively on the in-process tree (children and parents), and calling the same method.

Called from HandleAccessKey called from BrowserChild (mostly more confirmation this has been made fission-compatible).

Change DocShell tree usage to BrowsingContext intead.

Comment 1

[Chris Peterson [:cpeterson]]

Kannan says replacing nsIDocShellTreeItem calls should block enabling Fission in Nightly (M6).

Comment 2

[Chris Peterson [:cpeterson]]

We need to audit this use of the nsIDocShellTreeItem interface. With Fission enabled, Documents and nsDocShells for related frames, such as subframes and parent documents, may not be available within the current process and the corresponding nsIDocShellTreeItem methods will return null.

If this code is broken with Fission, fixing it blocks enabling Fission is Nightly.

If this code works as-is with Fission, we don't need to remove this usage of nsIDocShellTreeItem until when we remove nsIDocShellTreeItem entirely (bug 1607591) after we ship Fission MVP.

Fission documentation about replacing nsIDocShellTree Item:
https://wiki.mozilla.org/Project_Fission/DocShell_Tree_Replace

:farre's presentation with examples of replacing nsIDocShellTreeItem with BrowsingContext, WindowContext, SyncedContexts, and BrowsingContextGroup:
https://docs.google.com/presentation/d/1K4j6ngty64TZjJNS5qH-MBoOm3TI2dJedVsbH8jUhKE/edit#slide=id.g6e35225e5d_1_264

Comment 3

[Chris Peterson [:cpeterson]]

Auditing whether this use of nsIDocShellTreeItem breaks when Fission is enabled blocks Fission Nightly.