Implement SequencedWorkerPool::RunsTasksOnCurrentThread()

Implement SequencedWorkerPool::RunsTasksOnCurrentThread()

Store threads in a tid-indexed map instead of a vector.  Use that to
implement RunsTasksOnCurrentThread().

Expand TaskRunner test template to include test for
RunsTasksOnCurrentThread().

Move some utility classes/functions for the TaskRunner test template into
the internal namespace.

BUG=114329, 114327
TEST=

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=125798

[akalin, 2012-03-07 02:26:07]

+brettw for review

[akalin, 2012-03-07 21:13:18]

On 2012/03/07 02:26:07, akalin wrote:
> +brettw for review

ping!

[brettw, 2012-03-08 21:45:33]

LGTM.

Have you thought about putting the test template in base/test? This initially
confused me since I thought this was production code with an EXPECT in it.

[akalin, 2012-03-09 04:23:05]

On 2012/03/08 21:45:33, brettw wrote:
> LGTM.
> 
> Have you thought about putting the test template in base/test? This initially
> confused me since I thought this was production code with an EXPECT in it.

Oh, that might be a better place to put it.  I'll do that in a separate CL.