Merge to XFA: Extern in .cpp files is a code smell, part 1.

(cherry picked from commit 71c15a5e6652952a94ba3a3ef7ac0392e3a06962)
Original Review URL: https://codereview.chromium.org/1299963002 .

R=thestig@chromium.org
TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1301073003 .
33 files changed