IV. Clear Data Dialog Cleanup

Cleanup patch removing dead code after the new dialog shipped.

Bug 1856418 | D271909 | Reviewer: manuel

The Change

The old clear history dialog (sanitize.xhtml) and the preference privacy.sanitize.useOldClearHistoryDialog have been fully removed. The new dialog (sanitize_v2.xhtml) is now the only option.

Removed

UI Files:

• sanitize.xhtml
• clearSiteData.xhtml
• sanitize.js
• clearSiteData.js

Tests:

• browser_sanitizeDialog.js
• test_Sanitizer_interrupted.js
• Other old dialog test files

Preferences:

• privacy.sanitize.useOldClearHistoryDialog from StaticPrefList.yaml and firefox.js

Updated

• sanitizeDialog.js and Sanitizer.sys.mjs — removed conditional branches
• privacy.js — removed old dialog selection logic
• CacheObserver.h — removed C++ preference check
• Test files — removed old dialog preference settings
• Test manifests — removed old test entries
• jar.mn — removed old dialog files from packaging

What I Learned

1. Cleanup patches require thoroughness — Every reference must be found: prefs, tests, localization, conditionals
2. Always run lint before committing — ./mach lint --warnings --outgoing catches accidental file inclusions
3. Legacy code accumulates — Every feature flag eventually becomes tech debt; regular cleanup keeps the codebase maintainable