Standardize usage of virtual/override/final specifiers.

Standardize usage of virtual/override/final specifiers.

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.

BUG=417463
R=pauljensen@chromium.org

Committed: https://crrev.com/67be2b1f8dbb8fe664365ce33cd6ccf2832e0663
Cr-Commit-Position: refs/heads/master@{#301452}

[eroman, 2014-10-27 20:22:31]

eroman@chromium.org changed reviewers:
+ eroman@chromium.org

[eroman, 2014-10-27 20:22:32]

rslgtm.

Does the clang-format plugin now suggest these as well?

[eroman, 2014-10-27 20:22:53]

lgtm

[dcheng, 2014-10-27 20:25:40]

It doesn't autosuggest these, because it would cause compile errors on the clang
bots. The goal of these patches is to be able to enable these plugin warnings
eventually so it will suggest these edits.

[dcheng, 2014-10-27 20:25:51]

The CQ bit was checked by dcheng@chromium.org

[commit-bot: I haz the power, 2014-10-27 20:27:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/663043004/1

[commit-bot: I haz the power, 2014-10-27 21:48:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-27 21:48:51]

Patchset 1 (id:??) landed as
https://crrev.com/67be2b1f8dbb8fe664365ce33cd6ccf2832e0663
Cr-Commit-Position: refs/heads/master@{#301452}