Revert of Standardize usage of virtual/override/final in ipc/

Revert of Standardize usage of virtual/override/final in ipc/ (patchset #1 id:1 of https://codereview.chromium.org/645623006/)

Reason for revert:
Addressing reviewer comments in a followup patch.

Original issue's description:
> Standardize usage of virtual/override/final in ipc/
>
> This patch was automatically generated by applying clang fixit hints
> generated by the plugin to the source tree.
>
> BUG=417463
> TBR=agl@chromium.org
>
> Committed: https://crrev.com/39be52ebbd6681c7d79ad63e2a0ab028075af0c2
> Cr-Commit-Position: refs/heads/master@{#300481}

TBR=agl@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=417463
Committed: https://crrev.com/f3076af7e0dfc078e65039a0e6faebf9a7628a63
Cr-Commit-Position: refs/heads/master@{#300521}

[dcheng, 2014-10-21 17:58:18]

Created Revert of Standardize usage of virtual/override/final in ipc/

[commit-bot: I haz the power, 2014-10-21 18:00:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/669953003/1

[commit-bot: I haz the power, 2014-10-21 18:03:01]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-21 18:04:11]

Patchset 1 (id:??) landed as
https://crrev.com/f3076af7e0dfc078e65039a0e6faebf9a7628a63
Cr-Commit-Position: refs/heads/master@{#300521}