Just ran into this when doing an official build locally:

../../chrome/browser/android/offline_pages/request_coordinator_factory.cc:38:12:
error: unused variable 'kPreferUntriedRequest' [-Werror,-Wunused-const-variable]
const bool kPreferUntriedRequest = false;
^

Looks like the constants might need to be wrapped in "#if
!defined(OFFICIAL_BUILD)" as well. I'm not actually sure if any bots will catch
this, I don't think any of the release builders use clang.