Route resource dispatch tasks via the loading task queue

Route resource dispatch tasks via the loading task queue

This patch should make the main thread more responsive when the user
is interacting with the device while the page is loading.

Sherrifs if you see an uptick in blink layout test flakes this patch
might be to blame.

I tried to reproduce the flakes I saw in the try runs locally.
With the exception of fast/loader/subframe-removes-itself.html
I was not able to reproduce a flake, however judging by the flakiness
dashboard, that test is already slightly flaky.

BUG=391005
Committed: https://crrev.com/1838a81f74e6ef7a6cc9296bfec20ea1f0ff97a1
Cr-Commit-Position: refs/heads/master@{#313739}

[alex clarke (OOO till 29th), 2015-01-28 11:18:55]

alexclarke@chromium.org changed reviewers:
+ jochen@chromium.org, skyostil@chromium.org

[alex clarke (OOO till 29th), 2015-01-28 12:20:13]

On 2015/01/28 11:18:55, alexclarke1 wrote:

Looks like this patch may not go far enough, just done some tracing with this
patch enabled and I'm seeing some ChannelProxy::Context::OnDispatchMessage tasks
that are not on the LoadingTaskQueue.  I'll send out a revised version later.

[alex clarke (OOO till 29th), 2015-01-28 13:26:50]

I've set the IPC Sync Thread's listener task runner to be the loading task queue
too, which judging by traces fixes the issue.

PTAL

[jochen (gone - plz use gerrit), 2015-01-28 19:00:03]

lgtm

[alex clarke (OOO till 29th), 2015-01-29 11:18:33]

The CQ bit was checked by alexclarke@chromium.org

[commit-bot: I haz the power, 2015-01-29 11:19:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/882073002/20001

[commit-bot: I haz the power, 2015-01-29 12:13:39]

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

[commit-bot: I haz the power, 2015-01-29 12:13:40]

Try jobs failed on following builders:
  win8_chromium_rel on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win8_chromium_rel...)

[alex clarke (OOO till 29th), 2015-01-29 14:36:39]

The CQ bit was checked by alexclarke@chromium.org

[commit-bot: I haz the power, 2015-01-29 14:37:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/882073002/20001

[commit-bot: I haz the power, 2015-01-29 15:27:51]

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

[commit-bot: I haz the power, 2015-01-29 15:27:52]

Try jobs failed on following builders:
  linux_chromium_chromeos_rel_ng on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[alex clarke (OOO till 29th), 2015-01-29 17:33:40]

The CQ bit was checked by alexclarke@chromium.org

[commit-bot: I haz the power, 2015-01-29 17:34:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/882073002/40001

[commit-bot: I haz the power, 2015-01-29 18:25:37]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-01-29 18:26:31]

Patchset 3 (id:??) landed as
https://crrev.com/1838a81f74e6ef7a6cc9296bfec20ea1f0ff97a1
Cr-Commit-Position: refs/heads/master@{#313739}