ServiceWorker: Add running service worker check before claim a provider host.

ServiceWorker: Add running service worker check before claim a provider host.

A provider host which hosts a running service worker has its document URL
set to the script's URL now. So check it explicitly to avoid DCHECK fail.

BUG=459244
Committed: https://crrev.com/d565971b03e3414d6a43ac2fef95d88a0b65de55
Cr-Commit-Position: refs/heads/master@{#317988}

[xiang, 2015-02-25 02:44:29]

xiang.long@intel.com changed reviewers:
+ falken@chromium.org

[xiang, 2015-02-25 02:45:34]

PTAL, thanks.
I'm not sure whether a layout test is needed or not?

[falken, 2015-02-25 03:21:17]

On 2015/02/25 02:45:34, xiang wrote:
> PTAL, thanks.
> I'm not sure whether a layout test is needed or not?

LGTM

[xiang, 2015-02-25 04:49:48]

The CQ bit was checked by xiang.long@intel.com

[commit-bot: I haz the power, 2015-02-25 04:50:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/947953003/1

[commit-bot: I haz the power, 2015-02-25 05:49:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-25 05:49:40]

Patchset 1 (id:??) landed as
https://crrev.com/d565971b03e3414d6a43ac2fef95d88a0b65de55
Cr-Commit-Position: refs/heads/master@{#317988}