Fix virtual/override/final usage in Source/platform/.

Fix virtual/override/final usage in Source/platform/.

- We should specify just one of them to a function.
  This was done by the following command.
  % sed -i "" -E "s/virtual (.*) final/\1 final/g;
    s/virtual (.*) override/\1 override/g;
    s/override final/final/g" <files>
- Non-base virtual destructors should have |override| keywords.

This CL has no behavior changes.

BUG=417463
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198474

[tkent, 2015-07-08 03:46:11]

tkent@chromium.org changed reviewers:
+ keishi@chromium.org

[tkent, 2015-07-08 03:46:12]

Keishi, please review this.

[haraken, 2015-07-08 04:08:20]

LGTM

[keishi, 2015-07-08 04:09:24]

lgtm

[tkent, 2015-07-08 04:24:54]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2015-07-08 04:25:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1213003004/1

[commit-bot: I haz the power, 2015-07-08 06:52:55]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=198474