Bug 20497: Check if the browser should run in portable mode at runtime (Tor Browser)

Merge Info

Related Issues

• #20497 (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
  • Base-browser part is !534 (merged)

Issue Tracking

• Link resolved issues with appropriate Release Prep issue for changelog generation
  • This is the second time I work on that issue now. I don't know if we can close it, yet. Even though we now support both portable and system-install mode in base-browser, we still support only portable mode in Tor Browser (because of some nonsense that we need to fix on the tor-launcher commit, first). We might want an additional issue for the changelogs.

Change Description

This is my latest effort in making the portable directory patch better.

Actually, most of it should have been handled in !534 (merged) (the base-browser part), but Tor Browser has also some specific behavior that we needed to replicate (especially on macOS, which is the only OS on which we officially support system-install).

Developed on Linux, and tested on Linux (both a local dev build and on a full testbuild), on Windows full testbuild and on macOS full testbuild (macOS has some additional code enabled with #ifdef).

/cc @richard