ServiceWorker: Support navigator.serviceWorker.installing

ServiceWorker: Support navigator.serviceWorker.installing 

This change plumbs '.installing' and you will be able to access
an installing worker via 'navigator.serviceWorker.installing'.


BUG=379012
TEST=content_unittest --gtest_filter=ServiceWorker*
TEST=run_webkit_tests.py  http/tests/serviceworker/installing.html (http://crrev.com/372453002)
TEST=run_webkit_tests.py http/tests/serviceworker/waiting.html

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=281931

[nhiroki, 2014-07-04 09:54:03]

Ptal, thanks!

[falken, 2014-07-07 01:35:02]

LGTM

[nhiroki, 2014-07-08 06:39:11]

+tsepez@, could you review service_worker_messages.h ? Thanks.

[nhiroki, 2014-07-08 07:22:50]

On 2014/07/08 06:39:11, nhiroki wrote:
> +tsepez@, could you review service_worker_messages.h ? Thanks.

Let me remove tsepez@ from reviewers since he may be OOO.

[nhiroki, 2014-07-08 07:25:20]

+jschuh@, could you review messages.h? Thanks.

[jschuh, 2014-07-08 16:24:40]

ipc security lgtm (notes: browser -> renderer URLs and routing info).

[nhiroki, 2014-07-08 21:14:08]

The CQ bit was checked by nhiroki@chromium.org

[commit-bot: I haz the power, 2014-07-08 21:19:27]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/nhiroki@chromium.org/369013002/240001

[commit-bot: I haz the power, 2014-07-09 04:35:53]

Change committed as 281931