Mark some destructors as virtual.

Mark some destructors as virtual.

Since the classes have virtual functions.

BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=291510

[Steven Holte, 2014-08-22 19:06:23]

lgtm

[Alexei Svitkine (slow), 2014-08-22 19:11:08]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2014-08-22 19:14:31]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/asvitkine@chromium.org/497213002/1

[commit-bot: I haz the power, 2014-08-22 19:14:32]

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

[commit-bot: I haz the power, 2014-08-22 19:14:33]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Alexei Svitkine (slow), 2014-08-22 19:18:45]

+jwd

[jwd, 2014-08-22 20:09:23]

lgtm

[Alexei Svitkine (slow), 2014-08-22 20:32:13]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2014-08-22 20:32:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/asvitkine@chromium.org/497213002/1

[commit-bot: I haz the power, 2014-08-22 21:33:06]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_chromium_gn_compile_rel on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_chromiu...)

[commit-bot: I haz the power, 2014-08-22 21:39:13]

Committed patchset #1 (1) as 291510