[Offline Pages] Close race condition of multiple StartProcessing callers.

[Offline Pages] Close race condition of multiple StartProcessing callers.

Introduces new bool to track the starting/picking phase so that we avoid
concurrent pickers (and not overwrite the schedule_callback) in order to also
avoid the DCHECK that guards concurrent SendRequestToOffliner calls.

BUG=643455
Review-Url: https://codereview.chromium.org/2317893002
Cr-Commit-Position: refs/heads/master@{#416957}
(cherry picked from commit 81356643cfe6ffe145741fb4b8fef53a3db86a50)

R=dougarnett@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/f68a8dfdcc256445b040cb9cf0f447e1b8e39de7

[dewittj, 2016-09-08 18:43:48]

Description was changed from

==========
[Offline Pages] Close race condition of multiple StartProcessing callers.

Introduces new bool to track the starting/picking phase so that we avoid
concurrent pickers (and not overwrite the schedule_callback) in order to also
avoid the DCHECK that guards concurrent SendRequestToOffliner calls.

BUG=643455

Review-Url: https://codereview.chromium.org/2317893002
Cr-Commit-Position: refs/heads/master@{#416957}
(cherry picked from commit 81356643cfe6ffe145741fb4b8fef53a3db86a50)
==========

to

==========
[Offline Pages] Close race condition of multiple StartProcessing callers.

Introduces new bool to track the starting/picking phase so that we avoid
concurrent pickers (and not overwrite the schedule_callback) in order to also
avoid the DCHECK that guards concurrent SendRequestToOffliner calls.

BUG=643455

Review-Url: https://codereview.chromium.org/2317893002
Cr-Commit-Position: refs/heads/master@{#416957}
(cherry picked from commit 81356643cfe6ffe145741fb4b8fef53a3db86a50)
==========

[dewittj, 2016-09-08 18:43:48]

dewittj@chromium.org changed reviewers:
+ dimich@chromium.org, dougarnett@chromium.org

[dewittj, 2016-09-08 18:44:28]

ptal, this is the merge candidate

[dougarnett, 2016-09-08 18:57:54]

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

[dougarnett, 2016-09-08 18:57:54]

Justin, did you happen to grab any of the conflict detail?

[dougarnett, 2016-09-08 19:50:08]

This look like a good change but I didn't see where there might have been
conflicts with Pete's CL.

[dougarnett, 2016-09-08 19:55:06]

lgtm

I think I get it now

[dewittj, 2016-09-08 20:07:11]

On 2016/09/08 19:55:06, dougarnett wrote:
> lgtm
> 
> I think I get it now

Main issue is rename of callback function RequestNotPicked (renamed from
RequestQueueEmpty).  If you want you can do the same merge yourself by checking
out refs/branch-heads/2840 and trying to cherry-pick your original CL.

[dewittj, 2016-09-08 20:25:16]

Description was changed from

==========
[Offline Pages] Close race condition of multiple StartProcessing callers.

Introduces new bool to track the starting/picking phase so that we avoid
concurrent pickers (and not overwrite the schedule_callback) in order to also
avoid the DCHECK that guards concurrent SendRequestToOffliner calls.

BUG=643455

Review-Url: https://codereview.chromium.org/2317893002
Cr-Commit-Position: refs/heads/master@{#416957}
(cherry picked from commit 81356643cfe6ffe145741fb4b8fef53a3db86a50)
==========

to

==========
[Offline Pages] Close race condition of multiple StartProcessing callers.

Introduces new bool to track the starting/picking phase so that we avoid
concurrent pickers (and not overwrite the schedule_callback) in order to also
avoid the DCHECK that guards concurrent SendRequestToOffliner calls.

BUG=643455

Review-Url: https://codereview.chromium.org/2317893002
Cr-Commit-Position: refs/heads/master@{#416957}
(cherry picked from commit 81356643cfe6ffe145741fb4b8fef53a3db86a50)

R=dougarnett@chromium.org

Committed:
https://chromium.googlesource.com/chromium/src/+/f68a8dfdcc256445b040cb9cf0f4...
==========

[dewittj, 2016-09-08 20:25:17]

Committed patchset #1 (id:1) manually as
f68a8dfdcc256445b040cb9cf0f447e1b8e39de7.