Allow Blink to respond asynchronously to SW Push events (side 2/3)

Allow Blink to respond asynchronously to SW Push events (side 2/3)

This will be necessary once Push events support event.waitUntil to keep the
Service Worker alive until the Promise is resolved
(https://github.com/w3c/push-api/issues/85).

Depends on Chromium https://codereview.chromium.org/708913003
Required by Chromium https://codereview.chromium.org/707243003

BUG=430888, 401438
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185008

[johnme, 2014-11-07 18:43:56]

johnme@chromium.org changed reviewers:
+ michaeln@chromium.org, mkwst@chromium.org

[johnme, 2014-11-07 18:43:56]

michaeln@chromium.org: Please review the overall patch, and give OWNERS approval
for Source/modules/serviceworkers/

mkwst@chromium.org: Please give OWNERS approval for Source/web/ and public/web/.

Thanks!

[Mike West, 2014-11-07 19:14:15]

Assuming michaeln@ is happy with the patch, */web LGTM

[michaeln, 2014-11-08 00:18:37]

lgtm 2

[johnme, 2014-11-08 19:52:31]

The CQ bit was checked by johnme@chromium.org

[commit-bot: I haz the power, 2014-11-08 19:52:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/709103002/1

[commit-bot: I haz the power, 2014-11-08 20:54:57]

Committed patchset #1 (id:1) as 185008