Check for null RenderWidgetHostDelegate before canceling scroll bubble

Check for null RenderWidgetHostDelegate before canceling scroll bubble

There were instances of crashes during destruction with nested
WebContents, if an inter-process scroll bubble was in progress. This
patch verifies that there the WebContents hasn't been disconnected
from its RenderWidgetHosts before attempting to cancel scroll
bubbling and dereferencing the RenderWidgetHostDelegate pointer.

BUG=644306
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Committed: https://crrev.com/b5f9d8018a4b55c4c713c22def90aaf570c1dfee
Cr-Commit-Position: refs/heads/master@{#417054}

[kenrb, 2016-09-07 14:55:07]

Description was changed from

==========
Check for null RenderWidgetHostDelegate before canceling scroll bubble

There were instances of crashes during destruction with nested
WebContents, if an inter-process scroll bubble was in progress. This
patch verifies that there the WebContents hasn't been disconnected
from its RenderWidgetHosts before attempting to cancel scroll
bubbling and dereferencing the RenderWidgetHostDelegate pointer.

BUG=644306
==========

to

==========
Check for null RenderWidgetHostDelegate before canceling scroll bubble

There were instances of crashes during destruction with nested
WebContents, if an inter-process scroll bubble was in progress. This
patch verifies that there the WebContents hasn't been disconnected
from its RenderWidgetHosts before attempting to cancel scroll
bubbling and dereferencing the RenderWidgetHostDelegate pointer.

BUG=644306
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation
==========

[kenrb, 2016-09-07 14:55:12]

The CQ bit was checked by kenrb@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-07 14:55:35]

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

[kenrb, 2016-09-07 15:29:25]

The CQ bit was checked by kenrb@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-07 15:29:38]

Dry run: 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, 2016-09-07 16:25:09]

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

[commit-bot: I haz the power, 2016-09-07 16:25:10]

Dry run: This issue passed the CQ dry run.

[kenrb, 2016-09-07 16:44:39]

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

[kenrb, 2016-09-07 16:44:39]

nasko: PTAL?

I wasn't able to reproduce locally, since this is a fairly exceptional race
condition, and accordingly I don't think I can make a reliable test.

[nasko, 2016-09-07 18:22:02]

LGTM

[kenrb, 2016-09-07 20:24:04]

The CQ bit was checked by kenrb@chromium.org

[commit-bot: I haz the power, 2016-09-07 20:24:58]

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, 2016-09-07 21:45:07]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-09-07 21:47:30]

Description was changed from

==========
Check for null RenderWidgetHostDelegate before canceling scroll bubble

There were instances of crashes during destruction with nested
WebContents, if an inter-process scroll bubble was in progress. This
patch verifies that there the WebContents hasn't been disconnected
from its RenderWidgetHosts before attempting to cancel scroll
bubbling and dereferencing the RenderWidgetHostDelegate pointer.

BUG=644306
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation
==========

to

==========
Check for null RenderWidgetHostDelegate before canceling scroll bubble

There were instances of crashes during destruction with nested
WebContents, if an inter-process scroll bubble was in progress. This
patch verifies that there the WebContents hasn't been disconnected
from its RenderWidgetHosts before attempting to cancel scroll
bubbling and dereferencing the RenderWidgetHostDelegate pointer.

BUG=644306
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Committed: https://crrev.com/b5f9d8018a4b55c4c713c22def90aaf570c1dfee
Cr-Commit-Position: refs/heads/master@{#417054}
==========

[commit-bot: I haz the power, 2016-09-07 21:47:31]

Patchset 2 (id:??) landed as
https://crrev.com/b5f9d8018a4b55c4c713c22def90aaf570c1dfee
Cr-Commit-Position: refs/heads/master@{#417054}