Revert of cc: Implement shared worker contexts. (patchset #9 id:160001 of https:...

Revert of cc: Implement shared worker contexts. (patchset #9 id:160001 of https://codereview.chromium.org/1336733002/ )

Reason for revert:
Broke GPU rasterization on Mac OS; please see https://code.google.com/p/chromium/issues/detail?id=523411#c26 .

I'm really sorry -- I don't know how this got past the CQ.

Original issue's description:
> cc: Implement shared worker contexts.
>
> This moves the responsibility to call BindToCurrentThread/SetupLock out
> of cc::OutputSurface and to the maintainer of the (possibly) shared
> context.
>
> OutputSurface now needs to be destroyed on the same thread they
> were created. OutputSurface::DetachFromClient() can be used to
> destroy any resources that need to be destroyed on the thread
> that the OutputSurface has been bound to.
>
> BUG=523411
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
>
> Committed: https://crrev.com/a47ef41ea03d3a5b8965eb700b682ddf8a1f055a
> Cr-Commit-Position: refs/heads/master@{#349274}

TBR=danakj@chromium.org,piman@chromium.org,sievers@chromium.org,reveman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=523411

Review URL: https://codereview.chromium.org/1356463002

Cr-Commit-Position: refs/heads/master@{#349313}