mac: Prepare for -Wunused-functions.

Mostly involves deleting hundreds of lines of unused code.

BUG=315884
R=akalin@chromium.org, brettw@chromium.org, fischman@chromium.org, jamesr@chromium.org, sky@chromium.org, thestig@chromium.org
TBR=piman, youngki

Review URL: https://codereview.chromium.org/63153003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233646 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233646