Fix occasional crash in TryNextRequest

Fix occasional crash in TryNextRequest

If chrome is shut down, then a user deletes a request from a
notification, the scheduler callback will not be set, and we could
crash trying to inform it.  To fix this, when we start, set an
empty scheduler callback to receive the call, so we don't try
to call through a nullptr.

BUG=657111
Committed: https://crrev.com/1cc1225e5bcaeef6cfb059a479c8b0a492460cb7
Cr-Commit-Position: refs/heads/master@{#426847}

[Pete Williamson, 2016-10-21 00:30:10]

petewil@chromium.org changed reviewers:
+ dougarnett@chromium.org

[dougarnett, 2016-10-21 16:46:02]

lgtm

https://codereview.chromium.org/2429213009/diff/1/components/offline_pages/ba...
File components/offline_pages/background/request_coordinator.cc (right):

https://codereview.chromium.org/2429213009/diff/1/components/offline_pages/ba...
components/offline_pages/background/request_coordinator.cc:490: // TODO: Make
sure the scheduler callback is valid before running it.
wonder if we could base on processing_state != STOPPED ?

[Pete Williamson, 2016-10-21 17:08:59]

The CQ bit was checked by petewil@chromium.org

[commit-bot: I haz the power, 2016-10-21 17:09:24]

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, 2016-10-21 18:20:46]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-10-21 18:42:37]

Description was changed from

==========
Fix occasional crash in TryNextRequest

If chrome is shut down, then a user deletes a request from a
notification, the scheduler callback will not be set, and we could
crash trying to inform it.  To fix this, when we start, set an
empty scheduler callback to receive the call, so we don't try
to call through a nullptr.

BUG=64911
==========

to

==========
Fix occasional crash in TryNextRequest

If chrome is shut down, then a user deletes a request from a
notification, the scheduler callback will not be set, and we could
crash trying to inform it.  To fix this, when we start, set an
empty scheduler callback to receive the call, so we don't try
to call through a nullptr.

BUG=64911

Committed: https://crrev.com/1cc1225e5bcaeef6cfb059a479c8b0a492460cb7
Cr-Commit-Position: refs/heads/master@{#426847}
==========

[commit-bot: I haz the power, 2016-10-21 18:42:38]

Patchset 1 (id:??) landed as
https://crrev.com/1cc1225e5bcaeef6cfb059a479c8b0a492460cb7
Cr-Commit-Position: refs/heads/master@{#426847}

[Pete Williamson, 2016-10-21 21:43:09]

Description was changed from

==========
Fix occasional crash in TryNextRequest

If chrome is shut down, then a user deletes a request from a
notification, the scheduler callback will not be set, and we could
crash trying to inform it.  To fix this, when we start, set an
empty scheduler callback to receive the call, so we don't try
to call through a nullptr.

BUG=64911

Committed: https://crrev.com/1cc1225e5bcaeef6cfb059a479c8b0a492460cb7
Cr-Commit-Position: refs/heads/master@{#426847}
==========

to

==========
Fix occasional crash in TryNextRequest

If chrome is shut down, then a user deletes a request from a
notification, the scheduler callback will not be set, and we could
crash trying to inform it.  To fix this, when we start, set an
empty scheduler callback to receive the call, so we don't try
to call through a nullptr.

BUG=657111

Committed: https://crrev.com/1cc1225e5bcaeef6cfb059a479c8b0a492460cb7
Cr-Commit-Position: refs/heads/master@{#426847}
==========