Non-letterboxed window management migration to the RFPHelper

Merge Info

• Related Issues

  • #41695 (closed)
  • #41631 (closed)

• Backport Timeline

  • Immediate - patchsets for critical bug fixes or other major blocker (e.g. fixes for a 0-day exploit) OR patchsets with trivial changes which do not need testing (e.g. fixes for typos or fixes easily verified in a local developer build)
  • Next Minor Stable Release - patchset that needs to be verified in nightly before backport
  • Eventually - patchset that needs to be verified in alpha before backport
  • No Backport - patchset for the next major stable

• Upstream Merging

  • Merge to base-browser - typically for !fixups to patches in the base-browser branch, though sometimes new patches as well
    • NOTE: if your changeset includes patches to both base-browser and tor-browser please please make separate merge requests for each part

• Issue Tracking

  • Link resolved issues with appropriate Release Prep issue for changelog generation

Change Description

These 3 commits respectively:

1. implements a slight rounding of the browser element size using the same mechanism as letterboxing to offset the weird initial window sizes caused by non-standard pixel density configurations (#41631 (closed))
2. Removes the maximization warning from torbutton.js
3. Migrates the maximization warning to RFPHelper.jsm where, after this MR, all the window size related RFP features live.

2+3 above are #41695 (closed)