Revert of Reparent SWProcessManager onto SWContextWrapper.

Revert of Reparent SWProcessManager onto SWContextWrapper. (https://codereview.chromium.org/292973003/)

Reason for revert:
I suspect this broke ServiceWorkerDispatcherHostTest.EarlyContextDeletion on linux

Original issue's description:
> Reparent SWProcessManager onto SWContextWrapper.
> 
> This will allow Wrapper::Shutdown to drop all process references synchronously
> in a future change, which will make it possible to shutdown Chrome with service
> workers running and without hitting the DCHECK in
> ProfileDestroyer::DestroyProfileWhenAppropriate().
> 
> BUG=368570
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272839

TBR=falken@chromium.org,kinuko@chromium.org,jyasskin@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=368570
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272858

[jochen (gone - plz use gerrit), 2014-05-26 18:29:33]

Created Revert of Reparent SWProcessManager onto SWContextWrapper.

[commit-bot: I haz the power, 2014-05-26 18:30:32]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jochen@chromium.org/307443003/1

[commit-bot: I haz the power, 2014-05-26 18:31:55]

Change committed as 272858