Electron Releases

Description of Change

Closes #51041
Refs CL:6111160

The PDF viewer's "save with changes" feature uses
window.showSaveFilePicker(), but the PDF extension runs in a cross-origin iframe (chrome-extension:// inside the app's origin). Chromium's File System Access API blocks cross-origin subframes from showing file pickers unless the embedder explicitly allows them via ContentClient::IsFilePickerAllowedForCrossOriginSubframe().

Chrome overrides this in ChromeContentClient to allowlist the PDF extension origin, but Electron never did — so the picker was always blocked with a SecurityError.

This adds the same override to ElectronContentClient, allowing the built-in PDF extension origin to bypass the cross-origin check.

Checklist

• I have built and tested this change
• I have filled out the PR description
• I have reviewed and verified the changes
• npm test passes
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed an issue where saving edited PDF files would fail with a cross-origin SecurityError.