[ServiceWorker] Fix ASSERT failure in DocumentThreadableLoader::handleResponse().

[ServiceWorker] Fix ASSERT failure in DocumentThreadableLoader::handleResponse().

In current implementation, ASSERT(!m_fallbackRequestForServiceWorker) in
DocumentThreadableLoader::handleResponse fails while loading the data URL or sending OPTIONS request using XHR.

This is because:
 - m_fallbackRequestForServiceWorker is set in the constructor of DocumentThreadableLoader,
 - But the request is not handled by the ServiceWorker.
 - So DocumentThreadableLoader::handleResponse() is called with response.wasFetchedViaServiceWorker() == false.

This cl add the check of the URL scheme and the HTTP method in the constructor of DocumentThreadableLoader.

BUG=434603
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185624

[horo, 2014-11-19 12:42:28]

horo@chromium.org changed reviewers:
+ yhirano@chromium.org

[horo, 2014-11-19 12:42:29]

yhirano@
Could you please review this?

[yhirano, 2014-11-19 13:29:11]

lgtm

[horo, 2014-11-19 13:32:27]

horo@chromium.org changed reviewers:
+ mkwst@chromium.org

[horo, 2014-11-19 13:32:27]

mkwst@
Could you please review this?

[Mike West, 2014-11-19 16:20:22]

LGTM, thanks!

[horo, 2014-11-19 21:01:08]

The CQ bit was checked by horo@chromium.org

[commit-bot: I haz the power, 2014-11-19 21:01:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/726543008/1

[commit-bot: I haz the power, 2014-11-19 21:44:06]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=185624