Adds NULL checks in RenderFrameHostImpl::GetVisibilityState().

Adds NULL checks in RenderFrameHostImpl::GetVisibilityState().

BUG=501863
Committed: https://crrev.com/fb11060f7727a29dc9ca2ca5eef0274159def31a
Cr-Commit-Position: refs/heads/master@{#350274}

[Peter Beverloo, 2015-09-21 20:03:55]

peter@chromium.org changed reviewers:
+ kenrb@chromium.org, nasko@chromium.org

[Peter Beverloo, 2015-09-21 20:03:56]

+kenrb and nasko

This is not pretty, but it will work around the crash seen in 501863. Since the
crash is only observed through Push
(PushMessagingNotificationManager::DidGetNotificationsFromDatabase) I'd prefer
to localize a work-around there, but the used members aren't in the public
//content API, and adding APIs seems worse.

WDYT?

[kenrb, 2015-09-22 19:57:26]

lgtm. It would be nice if we could understand how it is getting in this state,
but I don't know what else we could do here and the crash needs to be fixed.

[nasko, 2015-09-22 22:39:27]

The bug update list numbers of crashes that are substantial. I would've expected
that we can repro this locally or get an idea of what could be the root cause
for this.

I do prefer us not crashing on users as much, so I'll LGTM this, but I would
like further investigations on this and not for it to linger around for ages.

[Peter Beverloo, 2015-09-22 23:32:09]

On 2015/09/22 22:39:27, nasko (slow to review) wrote:
> The bug update list numbers of crashes that are substantial. I would've
expected
> that we can repro this locally or get an idea of what could be the root cause
> for this.
> 
> I do prefer us not crashing on users as much, so I'll LGTM this, but I would
> like further investigations on this and not for it to linger around for ages.

Thank you. I've tried to repo on four devices locally and was unable to, but can
give it another go later this week. Let's figure out the details on the bug.

Putting this on the CQ before the tree goes bust tomorrow, with the merge and
all.

[Peter Beverloo, 2015-09-22 23:32:13]

The CQ bit was checked by peter@chromium.org

[commit-bot: I haz the power, 2015-09-22 23:34:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1355513003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1355513003/1

[commit-bot: I haz the power, 2015-09-23 00:25:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-23 00:26:44]

Patchset 1 (id:??) landed as
https://crrev.com/fb11060f7727a29dc9ca2ca5eef0274159def31a
Cr-Commit-Position: refs/heads/master@{#350274}