Remove support for specifying the number of available threads

Remove support for specifying the number of available threads

The embedder can control how many threads it wants to use via the
v8::Platform implementation. V8 internally doesn't spin up threads
anymore. If the embedder doesn't want to use any threads at all, it's
v8::Platform implementation must either run the background jobs on
the foreground thread, or the embedder should specify --predictable

BUG=none
R=yangguo@chromium.org
LOG=y

Committed: https://crrev.com/47cca4684e18c928d5d32b290b4c1314ac156953
Cr-Commit-Position: refs/heads/master@{#27833}

[Yang, 2015-04-15 06:37:52]

On 2015/04/14 15:06:40, jochen wrote:

lgtm.

Do I understand correctly that concurrency can be turned off completely if the
platform provides no threads? In that case, nothing weird would happen, right
(like waiting for a compile task that is never done).

[jochen (gone - plz use gerrit), 2015-04-15 07:08:04]

On 2015/04/15 at 06:37:52, yangguo wrote:
> On 2015/04/14 15:06:40, jochen wrote:
> 
> lgtm.
> 
> Do I understand correctly that concurrency can be turned off completely if the
platform provides no threads? In that case, nothing weird would happen, right
(like waiting for a compile task that is never done).

not quite.

the embedder would have to run the tasks on the foreground thread.

or specify --predictable

[jochen (gone - plz use gerrit), 2015-04-15 07:09:01]

updated the CL description to clarify this

[jochen (gone - plz use gerrit), 2015-04-15 07:14:10]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-04-15 07:14:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1064723005/1

[commit-bot: I haz the power, 2015-04-15 07:15:57]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-15 07:16:07]

Patchset 1 (id:??) landed as
https://crrev.com/47cca4684e18c928d5d32b290b4c1314ac156953
Cr-Commit-Position: refs/heads/master@{#27833}

[Michael Achenbach, 2015-04-15 09:02:41]

On 2015/04/15 07:16:07, I haz the power (commit-bot) wrote:
> Patchset 1 (id:??) landed as
> https://crrev.com/47cca4684e18c928d5d32b290b4c1314ac156953
> Cr-Commit-Position: refs/heads/master@{#27833}

Is this possibly the reason for some timeouts and crashes in layout tests, e.g.
http://build.chromium.org/p/client.v8/builders/V8-Blink%20Linux%2064/builds/3002
?