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

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

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/07903e579abf9f18d79935e1f531c7cd88503c58
Cr-Commit-Position: refs/heads/master@{#326456}

[ncarter (slow), 2015-04-23 03:22:21]

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

[Lei Zhang, 2015-04-23 04:51:36]

lgtm

[Lei Zhang, 2015-04-23 04:52:57]

The CQ bit was checked by thestig@chromium.org

[commit-bot: I haz the power, 2015-04-23 04:53:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1088763004/1

[commit-bot: I haz the power, 2015-04-23 04:56:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-23 04:57:50]

Patchset 1 (id:??) landed as
https://crrev.com/07903e579abf9f18d79935e1f531c7cd88503c58
Cr-Commit-Position: refs/heads/master@{#326456}