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

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

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/5c1d060ed293f8c882e1ba82c1c10c743167d0b5
Cr-Commit-Position: refs/heads/master@{#326454}

[ncarter (slow), 2015-04-22 21:09:35]

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

[Cait (Slow), 2015-04-23 00:03:27]

lgtm

[ncarter (slow), 2015-04-23 04:38:28]

The CQ bit was checked by nick@chromium.org

[commit-bot: I haz the power, 2015-04-23 04:39:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1106533003/1

[commit-bot: I haz the power, 2015-04-23 04:43:38]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-23 04:45:41]

Patchset 1 (id:??) landed as
https://crrev.com/5c1d060ed293f8c882e1ba82c1c10c743167d0b5
Cr-Commit-Position: refs/heads/master@{#326454}