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

Revert of Reland Call dispatcher's releaseRegistration when done with registrations (patchset #2 id:40001 of https://codereview.chromium.org/1290073003/ )

Reason for revert:
Speculatively reverting to fix crashes in http/tests/cache/cached-main-resource.html

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#showExpectations=true&tests=http%2Ftests%2Fcache%2Fcached-main-resource.html

Original issue's description:
> Reland Call dispatcher's releaseRegistration when done with registrations
> 
> Reland of https://codereview.chromium.org/1279323002/
> 
> OilPan objects can be garbage collected at any time, so it's necessary to check the pointers.
> 
> BUG=502214
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200657

TBR=jsbell@chromium.org,jkarlin@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=502214
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200663

[leviw_travelin_and_unemployed, 2015-08-17 20:10:37]

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

[commit-bot: I haz the power, 2015-08-17 20:10:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1288893004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1288893004/1

[commit-bot: I haz the power, 2015-08-17 20:11:40]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200663