Description of Change

Pass all required webPreferences (such as the list of preload scripts) via native mojo IPC as the command-line is shared when the same renderer process is hosting multiple BrowserWindows (scriptable popup with nativeWindowOpen: true for example).

Fixes #18466

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant documentation is changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Preload scripts configured for popups when handling the new-window event now work properly regardless of whether a new renderer process is hosting the contents (cross-origin) or the same renderer (same-origin).