The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/413675e9b667e07ae84a115268abedfdb7430740

commit 413675e9b667e07ae84a115268abedfdb7430740
Author: Josh Karlin <jkarlin@chromium.org>
Date: Wed Jun 06 17:02:59 2018

Run PrioritizedTaskRunner tasks with the same priority in posting order

What:
If two tasks have the same priority, they should run in posting order.

A second thing this CL does is fix a race in the unittests. I meant to block
the task runner before queueing up requests but failed to. Fixed here.

Why:
This can prevent hypothetical task starvation. It's also necessary for the
SimpleCachePrioritization control group to ensure that we maintain old
behavior.

Bug:  850085 
Change-Id: I1f259296604bf04ea33ecbee9ad3180f064c4266
Reviewed-on: https://chromium-review.googlesource.com/1088759
Commit-Queue: Josh Karlin <jkarlin@chromium.org>
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564933}
[modify] https://crrev.com/413675e9b667e07ae84a115268abedfdb7430740/net/base/prioritized_task_runner.cc
[modify] https://crrev.com/413675e9b667e07ae84a115268abedfdb7430740/net/base/prioritized_task_runner.h
[modify] https://crrev.com/413675e9b667e07ae84a115268abedfdb7430740/net/base/prioritized_task_runner_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cf61ddd65c0c26adfa89819fc1df16244dd7c8c4

commit cf61ddd65c0c26adfa89819fc1df16244dd7c8c4
Author: Findit <findit-for-me@appspot.gserviceaccount.com>
Date: Wed Jun 06 23:35:05 2018

Revert "Run PrioritizedTaskRunner tasks with the same priority in posting order"

This reverts commit 413675e9b667e07ae84a115268abedfdb7430740.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 564933 as the
culprit for failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtLzQxMzY3NWU5YjY2N2UwN2FlODRhMTE1MjY4YWJlZGZkYjc0MzA3NDAM

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.memory/Linux%20ChromiumOS%20MSan%20Tests/7480

Sample Failed Step: browser_tests

Original change's description:
> Run PrioritizedTaskRunner tasks with the same priority in posting order
> 
> What:
> If two tasks have the same priority, they should run in posting order.
> 
> A second thing this CL does is fix a race in the unittests. I meant to block
> the task runner before queueing up requests but failed to. Fixed here.
> 
> Why:
> This can prevent hypothetical task starvation. It's also necessary for the
> SimpleCachePrioritization control group to ensure that we maintain old
> behavior.
> 
> Bug:  850085 
> Change-Id: I1f259296604bf04ea33ecbee9ad3180f064c4266
> Reviewed-on: https://chromium-review.googlesource.com/1088759
> Commit-Queue: Josh Karlin <jkarlin@chromium.org>
> Reviewed-by: Maks Orlovich <morlovich@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#564933}

Change-Id: Id4930090c0026aefa9d92bb8871e809a3fcfa124
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  850085 
Reviewed-on: https://chromium-review.googlesource.com/1089892
Cr-Commit-Position: refs/heads/master@{#565096}
[modify] https://crrev.com/cf61ddd65c0c26adfa89819fc1df16244dd7c8c4/net/base/prioritized_task_runner.cc
[modify] https://crrev.com/cf61ddd65c0c26adfa89819fc1df16244dd7c8c4/net/base/prioritized_task_runner.h
[modify] https://crrev.com/cf61ddd65c0c26adfa89819fc1df16244dd7c8c4/net/base/prioritized_task_runner_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ae585b6551b8dd2f75da7203727b62140d20162d

commit ae585b6551b8dd2f75da7203727b62140d20162d
Author: Josh Karlin <jkarlin@chromium.org>
Date: Thu Jun 07 14:27:16 2018

Reland of "Run PrioritizedTaskRunner tasks with the same priority in posting order"

Reland of: https://chromium-review.googlesource.com/c/chromium/src/+/1088759

I forgot to initialize a member variable.

Bug:  850085 
Change-Id: Idae7c9fe8f658f5d6657881354d6254c302c53e6
Reviewed-on: https://chromium-review.googlesource.com/1090811
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Commit-Queue: Josh Karlin <jkarlin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565260}
[modify] https://crrev.com/ae585b6551b8dd2f75da7203727b62140d20162d/net/base/prioritized_task_runner.cc
[modify] https://crrev.com/ae585b6551b8dd2f75da7203727b62140d20162d/net/base/prioritized_task_runner.h
[modify] https://crrev.com/ae585b6551b8dd2f75da7203727b62140d20162d/net/base/prioritized_task_runner_unittest.cc