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

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

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 manually generated using a regex and a text editor.

BUG=417463
Committed: https://crrev.com/e81b3346126a4f586992ed502256eba5b43f1e19
Cr-Commit-Position: refs/heads/master@{#326453}

[ncarter (slow), 2015-04-23 04:21:00]

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

[ncarter (slow), 2015-04-23 04:21:01]

zelidrag: please review

[hashimoto, 2015-04-23 04:22:51]

hashimoto@chromium.org changed reviewers:
+ hashimoto@chromium.org

[hashimoto, 2015-04-23 04:22:51]

lgtm

[ncarter (slow), 2015-04-23 04:38:21]

The CQ bit was checked by nick@chromium.org

[commit-bot: I haz the power, 2015-04-23 04:39:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1101763002/1

[commit-bot: I haz the power, 2015-04-23 04:43:24]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-23 04:44:32]

Patchset 1 (id:??) landed as
https://crrev.com/e81b3346126a4f586992ed502256eba5b43f1e19
Cr-Commit-Position: refs/heads/master@{#326453}