DocsUI: Disable debug logging by default.

Per the platform team, we shouldn't enable debug logging automatically
in debug builds because it increases log-spam.  Just disable the flag
and enable it manually when needed.

Add some ifs to make sure all our debug logging is properly removed.

BUG=27380154

Change-Id: I8338f226c07affdb65970c7cb14f1e6aae036934