As your log shows, libflac12t64 and libopenh264-7 were installed from testing, not sid. Sid has libflac14 and libopenh264-8.
- Bug#1099210: chromium: Uninstallable on sid due to old deps Guillem Jover
- Bug#1099210: chromium: Uninstallable on sid due to old... Tobias Frost
- Bug#1099210: chromium: Uninstallable on sid due to... Fiona Klute
- Bug#1099210: chromium: Uninstallable on sid du... Tobias Frost
- Bug#1099210: chromium: Uninstallable on sid due to... Andres Salomon
- Bug#1099210: chromium: Uninstallable on sid du... Sjoerd Simons
