Standardize usage of virtual/override/final in ipc/

Standardize usage of virtual/override/final in ipc/

The Google C++ style guide states:

  Explicitly annotate overrides of virtual functions or virtual
  destructors with an override or (less frequently) final specifier.
  Older (pre-C++11) code will use the virtual keyword as an inferior
  alternative annotation. For clarity, use exactly one of override,
  final, or virtual when declaring an override.

To better conform to these guidelines, the following constructs have
been rewritten:

- if a base class has a virtual destructor, then:
    virtual ~Foo();                   ->  ~Foo() override;
- virtual void Foo() override;        ->  void Foo() override;
- virtual void Foo() override final;  ->  void Foo() final;

This patch was automatically generated. The clang plugin can generate
fixit hints, which are suggested edits when it is 100% sure it knows how
to fix a problem. The hints from the clang plugin were applied to the
source tree using the tool in https://codereview.chromium.org/598073004.

Several formatting edits by clang-format were manually reverted, due to
mangling of some of the more complicate IPC macros.

BUG=417463
R=agl@chromium.org

Committed: https://crrev.com/fe61fca6faca13c54768ee131dc79c8e06421097
Cr-Commit-Position: refs/heads/master@{#300623}

[dcheng, 2014-10-21 18:55:37]

I think I've reverted all the clang-format changes that you objected in
https://codereview.chromium.org/645623006/

[agl, 2014-10-22 00:34:23]

The CQ bit was checked by agl@chromium.org

[agl, 2014-10-22 00:34:24]

lgtm

[commit-bot: I haz the power, 2014-10-22 00:36:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/666493005/1

[commit-bot: I haz the power, 2014-10-22 01:25:40]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-10-22 01:25:41]

Try jobs failed on following builders:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[dcheng, 2014-10-22 01:33:07]

The CQ bit was checked by dcheng@chromium.org

[commit-bot: I haz the power, 2014-10-22 01:35:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/666493005/1

[commit-bot: I haz the power, 2014-10-22 02:30:19]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-22 04:05:33]

Patchset 1 (id:??) landed as
https://crrev.com/fe61fca6faca13c54768ee131dc79c8e06421097
Cr-Commit-Position: refs/heads/master@{#300623}