Make TracingStatus an immutable value.

This change also removes weakness related code which will be implemented differently in a subsequent CL.

BUG=334149
R=ager@chromium.org

Review URL: https://codereview.chromium.org/182313006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254131 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254131
Remove keychain_reauthorize.

This code was used when we changed our signing certificate. By now, all
Keychain entries have been migrated to the new certificate. If we ever need
this again, we can resurrect it from version control history.

BUG=347622
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/183713003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254132 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254132