Update {virtual,override} to follow C++11 style in tools.

Update {virtual,override} to follow C++11 style in tools.

The Google style guide states that only one of {virtual,override,final} should be used for each declaration, since override implies virtual and final implies both virtual and override.

This patch was ironically generated using a regex and a text editor.

BUG=417463
Committed: https://crrev.com/8787d39596aa89b0e83dc89b361e1eb80253e246
Cr-Commit-Position: refs/heads/master@{#326452}

[ncarter (slow), 2015-04-23 04:07:11]

nick@chromium.org changed reviewers:
+ thakis@chromium.org

[ncarter (slow), 2015-04-23 04:07:11]

thakis -- please review

[Nico, 2015-04-23 04:36:17]

lgtm

[ncarter (slow), 2015-04-23 04:38:02]

The CQ bit was checked by nick@chromium.org

[commit-bot: I haz the power, 2015-04-23 04:38:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1051643003/1

[commit-bot: I haz the power, 2015-04-23 04:42:27]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-23 04:44:30]

Patchset 1 (id:??) landed as
https://crrev.com/8787d39596aa89b0e83dc89b361e1eb80253e246
Cr-Commit-Position: refs/heads/master@{#326452}