Standardize usage of virtual/override/final specifiers in base/.

Standardize usage of virtual/override/final specifiers in base/.

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
Committed: https://crrev.com/8aef3761e6ff2a3315d23810187e5f52462db30f
Cr-Commit-Position: refs/heads/master@{#309527}

[dcheng, 2014-12-22 21:38:22]

dcheng@chromium.org changed reviewers:
+ thakis@chromium.org

[dcheng, 2014-12-22 21:38:23]

Hoping to enable the strict version of these checks on at least several
platforms while the tree is a little more quiet.

[Nico, 2014-12-22 22:05:42]

lgtm, but what's with all those empty overrides? Can we remove them? Or am I
dense?

https://codereview.chromium.org/804533005/diff/1/base/files/file_path_unittes...
File base/files/file_path_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/files/file_path_unittes...
base/files/file_path_unittest.cc:53: void SetUp() override {
PlatformTest::SetUp(); }
This doesn't have any effect. Can FilePathTest just be removed?

https://codereview.chromium.org/804533005/diff/1/base/sequence_checker_unitte...
File base/sequence_checker_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/sequence_checker_unitte...
base/sequence_checker_unittest.cc:59: ~SequenceCheckerTest() override {}
remove?

https://codereview.chromium.org/804533005/diff/1/base/system_monitor/system_m...
File base/system_monitor/system_monitor_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/system_monitor/system_m...
base/system_monitor/system_monitor_unittest.cc:22: ~SystemMonitorTest() override
{}
remove?

https://codereview.chromium.org/804533005/diff/1/base/task/cancelable_task_tr...
File base/task/cancelable_task_tracker_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/task/cancelable_task_tr...
base/task/cancelable_task_tracker_unittest.cc:350:
~CancelableTaskTrackerDeathTest() override {}
remove?

https://codereview.chromium.org/804533005/diff/1/base/threading/sequenced_wor...
File base/threading/sequenced_worker_pool_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/threading/sequenced_wor...
base/threading/sequenced_worker_pool_unittest.cc:186: ~SequencedWorkerPoolTest()
override {}
remove?

https://codereview.chromium.org/804533005/diff/1/base/threading/sequenced_wor...
base/threading/sequenced_worker_pool_unittest.cc:188: void SetUp() override {}
remove?

[dcheng, 2014-12-22 22:41:26]

https://codereview.chromium.org/804533005/diff/1/base/sequence_checker_unitte...
File base/sequence_checker_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/sequence_checker_unitte...
base/sequence_checker_unittest.cc:59: ~SequenceCheckerTest() override {}
On 2014/12/22 at 22:05:42, Nico wrote:
> remove?

Done.

https://codereview.chromium.org/804533005/diff/1/base/system_monitor/system_m...
File base/system_monitor/system_monitor_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/system_monitor/system_m...
base/system_monitor/system_monitor_unittest.cc:22: ~SystemMonitorTest() override
{}
On 2014/12/22 at 22:05:42, Nico wrote:
> remove?

Done.

https://codereview.chromium.org/804533005/diff/1/base/task/cancelable_task_tr...
File base/task/cancelable_task_tracker_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/task/cancelable_task_tr...
base/task/cancelable_task_tracker_unittest.cc:350:
~CancelableTaskTrackerDeathTest() override {}
On 2014/12/22 at 22:05:42, Nico wrote:
> remove?

Done.

https://codereview.chromium.org/804533005/diff/1/base/threading/sequenced_wor...
File base/threading/sequenced_worker_pool_unittest.cc (right):

https://codereview.chromium.org/804533005/diff/1/base/threading/sequenced_wor...
base/threading/sequenced_worker_pool_unittest.cc:186: ~SequencedWorkerPoolTest()
override {}
On 2014/12/22 at 22:05:42, Nico wrote:
> remove?

Done.

https://codereview.chromium.org/804533005/diff/1/base/threading/sequenced_wor...
base/threading/sequenced_worker_pool_unittest.cc:188: void SetUp() override {}
On 2014/12/22 at 22:05:42, Nico wrote:
> remove?

Done.

[dcheng, 2014-12-23 01:21:30]

The CQ bit was checked by dcheng@chromium.org

[commit-bot: I haz the power, 2014-12-23 01:22:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/804533005/20001

[commit-bot: I haz the power, 2014-12-23 02:57:14]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-12-23 02:58:00]

Patchset 2 (id:??) landed as
https://crrev.com/8aef3761e6ff2a3315d23810187e5f52462db30f
Cr-Commit-Position: refs/heads/master@{#309527}