Revert of Call dispatcher's releaseRegistration when done with registrations

Revert of Call dispatcher's releaseRegistration when done with registrations (patchset #4 id:60001 of https://codereview.chromium.org/1279323002/ )

Reason for revert:
Reverting because it causes a crash in http/tests/background_sync/oneshot.html


https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Leak/builds/13337
https://storage.googleapis.com/chromium-layout-test-archives/WebKit_Linux_Leak/13337/layout-test-results/results.html

Original issue's description:
> Call dispatcher's releaseRegistration when done with them
> 
> With this series of patches, the BackgroundSyncManager expects clients
> to call ReleaseRegistration once no longer referencing them. This CL
> has Blink call releaseRegistration when the SyncRegistration and
> PeriodicRegistration are deleted.
> 
> Patch 1 [Blink]: this
> Patch 2 [Browser]: https://codereview.chromium.org/1282013004
> Patch 3 [Blink cleanup]: https://codereview.chromium.org/1285653002
> 
> BUG=502214
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200504

TBR=iclelland@chromium.org,jsbell@chromium.org,jkarlin@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=502214
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200544

[cbiesinger, 2015-08-14 16:05:36]

Created Revert of Call dispatcher's releaseRegistration when done with
registrations

[commit-bot: I haz the power, 2015-08-14 16:05:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1287343004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1287343004/1

[commit-bot: I haz the power, 2015-08-14 16:06:08]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200544