Check for a null callback in RendererSurfaceViewManager

Check for a null callback in RendererSurfaceViewManager

Now RSVM ignores surface created messages if there's no
outstanding request instead of trying to call a null
callback.

BUG=627453
Committed: https://crrev.com/abac0bdc0db93d2dba82b057222626506ec52533
Cr-Commit-Position: refs/heads/master@{#405322}

[watk, 2016-07-12 22:26:49]

Description was changed from

==========
Check for a null callback in RendererSurfaceViewManager

Crash reports indicate that it's possible for a surface creation reply
to be delivered.

BUG=627453
==========

to

==========
Check for a null callback in RendererSurfaceViewManager

Now RSVM ignores surface created messages if there's no
outstanding request instead of trying to call a null
callback.

BUG=627453
==========

[watk, 2016-07-12 22:26:50]

watk@chromium.org changed reviewers:
+ dalecurtis@chromium.org

[watk, 2016-07-13 18:01:18]

I believe this can happen if we manage to send two surface requests before there
are any replies.

i.e., enter/exit/enter-> will send two requests, but the latter clobbers the
first. The first response clears the callback. The second response hits a null
callback.

This change will fix the crash in a simple way so we can merge to 52. It doesn't
result in 100% correct behavior, but the failure mode is a) really hard to
trigger, and b)  benign.

I'll work a correct fix afterwards.

[DaleCurtis, 2016-07-13 20:48:33]

lgtm

[watk, 2016-07-13 20:55:51]

The CQ bit was checked by watk@chromium.org

[commit-bot: I haz the power, 2016-07-13 20:56:54]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-13 22:48:36]

Description was changed from

==========
Check for a null callback in RendererSurfaceViewManager

Now RSVM ignores surface created messages if there's no
outstanding request instead of trying to call a null
callback.

BUG=627453
==========

to

==========
Check for a null callback in RendererSurfaceViewManager

Now RSVM ignores surface created messages if there's no
outstanding request instead of trying to call a null
callback.

BUG=627453
==========

[commit-bot: I haz the power, 2016-07-13 22:48:37]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-13 22:49:06]

CQ bit was unchecked.

[commit-bot: I haz the power, 2016-07-13 22:50:27]

Description was changed from

==========
Check for a null callback in RendererSurfaceViewManager

Now RSVM ignores surface created messages if there's no
outstanding request instead of trying to call a null
callback.

BUG=627453
==========

to

==========
Check for a null callback in RendererSurfaceViewManager

Now RSVM ignores surface created messages if there's no
outstanding request instead of trying to call a null
callback.

BUG=627453

Committed: https://crrev.com/abac0bdc0db93d2dba82b057222626506ec52533
Cr-Commit-Position: refs/heads/master@{#405322}
==========

[commit-bot: I haz the power, 2016-07-13 22:50:28]

Patchset 1 (id:??) landed as
https://crrev.com/abac0bdc0db93d2dba82b057222626506ec52533
Cr-Commit-Position: refs/heads/master@{#405322}