Make SyncStartupTracker::Observer destructor virtual

Make SyncStartupTracker::Observer destructor virtual

Instances of SyncStartupTracker::Observer subclasses are likely to be
deleted through a SyncStartupTracker::Observer pointer.

While we are here, also put the include of sync_startup_tracker.h first
in sync_startup_tracker.cc for reasons stated in the style guide.

R=atwilson@chromium.org
BUG=

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=257502

[wdzierzanowski, 2014-03-17 09:21:59]

Hi Andrew,

Could you take a look please?

[Andrew T Wilson (Slow), 2014-03-17 09:36:55]

lgtm

[wdzierzanowski, 2014-03-17 09:43:20]

The CQ bit was checked by wdzierzanowski@opera.com

[commit-bot: I haz the power, 2014-03-17 09:43:23]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wdzierzanowski@opera.com/197243002/1

[commit-bot: I haz the power, 2014-03-17 09:44:45]

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

[commit-bot: I haz the power, 2014-03-17 09:44:46]

Try jobs failed on following builders:
  tryserver.chromium on linux_chromium_clang_dbg

[wdzierzanowski, 2014-03-17 11:40:58]

On 2014/03/17 09:44:46, I haz the power (commit-bot) wrote:
> Try jobs failed on following builders:
>   tryserver.chromium on linux_chromium_clang_dbg

Retrying as the failures appear unrelated to my changes...

[wdzierzanowski, 2014-03-17 11:41:05]

The CQ bit was checked by wdzierzanowski@opera.com

[commit-bot: I haz the power, 2014-03-17 11:41:14]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wdzierzanowski@opera.com/197243002/1

[commit-bot: I haz the power, 2014-03-17 12:58:48]

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

[commit-bot: I haz the power, 2014-03-17 12:58:49]

Try jobs failed on following builders:
  tryserver.chromium on mac_chromium_rel

[wdzierzanowski, 2014-03-17 14:11:31]

The CQ bit was checked by wdzierzanowski@opera.com

[commit-bot: I haz the power, 2014-03-17 14:11:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wdzierzanowski@opera.com/197243002/1

[commit-bot: I haz the power, 2014-03-17 20:59:37]

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

[commit-bot: I haz the power, 2014-03-17 20:59:37]

Commit queue rejected this change because the description was changed
between the time the change entered the commit queue and the time it
was ready to commit. You can safely check the commit box again.

[wdzierzanowski, 2014-03-17 21:44:36]

The CQ bit was checked by wdzierzanowski@opera.com

[commit-bot: I haz the power, 2014-03-17 21:45:32]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wdzierzanowski@opera.com/197243002/1

[commit-bot: I haz the power, 2014-03-17 21:53:03]

Change committed as 257502