-Wunused-functions for linux, android, chromeos

BUG=315884
TBR=hans@chromium.org

Review URL: https://codereview.chromium.org/62983004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234407 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234407