Fix style checker errors after https://codereview.chromium.org/1263403002/

Functions marked 'override' should not be marked 'virtual' also.

BUG=82385,516402
TBR=wittman

Review URL: https://codereview.chromium.org/1313543002 .

Cr-Commit-Position: refs/heads/master@{#345021}
1 file changed