Fix for crash in GuestViewBase::FindReply.

Fix for crash in GuestViewBase::FindReply.

There are two problems here:

1) The GuestViewBase received a FindReply while its WebContents was in the process of being destroyed. This patch adds a check in WebContentsImpl::NotifyFindReply to prevent this.

2) During destruction of GuestViewBase, there is a period of time when there is no owner WebContents, but attached() still returns true. This patch ensures that that attached() will return false as soon as |owner_web_contents_| is cleared.

BUG=642733
Committed: https://crrev.com/60b5d837275657c6d1cd0e110c833851b8d154ad
Cr-Commit-Position: refs/heads/master@{#415697}

[paulmeyer, 2016-08-31 16:11:16]

paulmeyer@chromium.org changed reviewers:
+ nick@chromium.org

[paulmeyer, 2016-08-31 16:11:16]

+nick@

[ncarter (slow), 2016-08-31 16:45:24]

lgtm

[paulmeyer, 2016-08-31 17:33:10]

The CQ bit was checked by paulmeyer@chromium.org

[commit-bot: I haz the power, 2016-08-31 17:33:47]

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, 2016-08-31 18:46:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-31 18:50:16]

Description was changed from

==========
Fix for crash in GuestViewBase::FindReply.

There are two problems here:

1) The GuestViewBase received a FindReply while its WebContents was in the
process of being destroyed. This patch adds a check in
WebContentsImpl::NotifyFindReply to prevent this.

2) During destruction of GuestViewBase, there is a period of time when there is
no owner WebContents, but attached() still returns true. This patch ensures that
that attached() will return false as soon as |owner_web_contents_| is cleared.

BUG=642733
==========

to

==========
Fix for crash in GuestViewBase::FindReply.

There are two problems here:

1) The GuestViewBase received a FindReply while its WebContents was in the
process of being destroyed. This patch adds a check in
WebContentsImpl::NotifyFindReply to prevent this.

2) During destruction of GuestViewBase, there is a period of time when there is
no owner WebContents, but attached() still returns true. This patch ensures that
that attached() will return false as soon as |owner_web_contents_| is cleared.

BUG=642733

Committed: https://crrev.com/60b5d837275657c6d1cd0e110c833851b8d154ad
Cr-Commit-Position: refs/heads/master@{#415697}
==========

[commit-bot: I haz the power, 2016-08-31 18:50:17]

Patchset 1 (id:??) landed as
https://crrev.com/60b5d837275657c6d1cd0e110c833851b8d154ad
Cr-Commit-Position: refs/heads/master@{#415697}