Revert of Revert of Fix RemoteFrame detachment to signal its client. (patchset #1 id:1 of https://codereview.chromium.org/699053004/)

Reason for revert:
Reverting the revert. This turned out not to be the cause of https://code.google.com/p/chromium/issues/detail?id=431608

Original issue's description:
> Revert of Fix RemoteFrame detachment to signal its client. (patchset #1 id:1 of https://codereview.chromium.org/712653002/)
> 
> Reason for revert:
> Speculative revert to attempt to fix https://code.google.com/p/chromium/issues/detail?id=431608
> 
> Original issue's description:
> > Fix RemoteFrame detachment to signal its client.
> > 
> > We were seeing crashes in checkFrameCountConsistency() because during
> > RemoteFrame detachment the client was not getting signalled to modify
> > the frame tree, resulting in inconsistent state. This CL corrects that
> > problem.
> > 
> > BUG=430972
> > 
> > Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184987
> 
> TBR=japhet@chromium.org,dcheng@chromium.org,kenrb@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=430972
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185015

TBR=japhet@chromium.org,dcheng@chromium.org,kenrb@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=430972

Review URL: https://codereview.chromium.org/709363002

git-svn-id: svn://svn.chromium.org/blink/trunk@185018 bbb929c8-8fbe-4397-9dbb-9b2b20218538