cc: Associate scheduled tasks with a prepare tiles call.

cc: Associate scheduled tasks with a prepare tiles call.

This patch adds a count of prepare tiles. As well, any task that is
created as a result of a prepare tiles gets the number of that prepare
tiles. This can be used to determine which tasks came from which prepare
tiles. Note that a further prepare tiles that would reuse a task does
not modify the id. That is the id still refers to the prepare tile that
created the task.

R=danakj
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/9da577a9c2b932e36e2ec22e473d7458ba3fe97b
Cr-Commit-Position: refs/heads/master@{#336070}

[vmpstr, 2015-06-24 22:03:57]

Please take a look.

[danakj, 2015-06-24 22:06:19]

> tiles. This can be used to allocate which tasks came from which prepare

s/allocate/determine/ ?

[danakj, 2015-06-24 22:06:46]

LGTM

[vmpstr, 2015-06-24 22:09:41]

The CQ bit was checked by vmpstr@chromium.org

[vmpstr, 2015-06-24 22:10:08]

The CQ bit was unchecked by vmpstr@chromium.org

[vmpstr, 2015-06-24 22:10:55]

The CQ bit was checked by vmpstr@chromium.org

[commit-bot: I haz the power, 2015-06-24 22:12:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1208683002/1

[commit-bot: I haz the power, 2015-06-24 22:31:27]

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

[commit-bot: I haz the power, 2015-06-24 22:31:28]

Exceeded global retry quota

[vmpstr, 2015-06-24 22:32:22]

The CQ bit was checked by vmpstr@chromium.org

[commit-bot: I haz the power, 2015-06-24 22:34:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1208683002/1

[commit-bot: I haz the power, 2015-06-24 22:46:30]

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

[commit-bot: I haz the power, 2015-06-24 22:46:32]

Exceeded global retry quota

[vmpstr, 2015-06-25 00:05:21]

The CQ bit was checked by vmpstr@chromium.org

[commit-bot: I haz the power, 2015-06-25 00:06:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1208683002/1

[commit-bot: I haz the power, 2015-06-25 02:11:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-25 02:12:14]

Patchset 1 (id:??) landed as
https://crrev.com/9da577a9c2b932e36e2ec22e473d7458ba3fe97b
Cr-Commit-Position: refs/heads/master@{#336070}