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

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

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/e4784434857731fd46a2ecdf0c132561ff6674a3
Cr-Commit-Position: refs/heads/master@{#326505}

[ncarter (slow), 2015-04-23 03:51:28]

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

[ncarter (slow), 2015-04-23 03:51:29]

dmichael: Please review this boring change.

[ncarter (slow), 2015-04-23 03:52:08]

nick@chromium.org changed reviewers:
- dmichael@chromium.org

[ncarter (slow), 2015-04-23 03:52:33]

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

[ncarter (slow), 2015-04-23 03:52:33]

bbudge: Please review this boring change.

[bbudge, 2015-04-23 13:35:03]

Let's hope it's boring. LGTM

[ncarter (slow), 2015-04-23 13:52:33]

The CQ bit was checked by nick@chromium.org

[commit-bot: I haz the power, 2015-04-23 13:52:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1097393007/40001

[commit-bot: I haz the power, 2015-04-23 14:01:56]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-04-23 14:03:19]

Patchset 3 (id:??) landed as
https://crrev.com/e4784434857731fd46a2ecdf0c132561ff6674a3
Cr-Commit-Position: refs/heads/master@{#326505}