Suppress 4 findbugs issues in tooling-only code.

BUG=338966
TBR=andrehayden@chromium.org

Review URL: https://codereview.chromium.org/146833022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247610 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247610