Support new local-network-access permissions policy on iframes

Summary

As discovered in this RFH (Internal) users in Chrome 142 are unable to open GitLab Duo in the WebIDE. Users will get a The webview didn't initialize in 10000ms in WebIDE due to new local-network-access security policies. This does not happen in other browsers.

This was recently fixed in VS Code but required a fix to our fork for the GitLab WebIDE.

• https://github.com/microsoft/vscode/pull/278185
• https://github.com/microsoft/vscode/issues/278184
• https://developer.chrome.com/blog/local-network-access

What is the current bug behavior?

Duo Chat in WebIDE fails to initialize in Chrome 142 with the error The webview didn't initialize in 10000ms

What is the expected correct behavior?

Duo Chat should load in the WebIDE in Chrome 142.

Relevant logs and/or screenshots

Relevant information in https://gitlab.com/gitlab-com/request-for-help/-/work_items/3791

Possible fixes

• https://www.paulserban.eu/blog/post/demystifying-nested-iframes-and-the-allowlocal-network-access-attribute-in-chrome/

Patch release information for backports

If the bug fix needs to be backported in a patch release to a version under the maintenance policy, please follow the steps on the patch release runbook for GitLab engineers.

Refer to the internal "Release Information" dashboard for information about the next patch release, including the targeted versions, expected release date, and current status.

High-severity bug remediation

To remediate high-severity issues requiring an internal release for single-tenant SaaS instances, refer to the internal release process for engineers.