Merge to XFA:  Fix a bunch of -Wunused-but-set-variable warnings.

Also fix a few nits and other errors along the way.

Review URL: https://codereview.chromium.org/1098583002
Review URL: https://codereview.chromium.org/1135713004

(cherry picked from commit f0a169e6fd5718995fa6ef8749c8d16cdad84985)
(cherry picked from commit 470408c2ffe71e99cebad0d1d6887f1723f02cef)

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1133453006
10 files changed