Revert 168890 "Make DOMWrapperWorld::current() callable from wor..."

I mis-committed this CL without passing try bots.
I'll revert it and reland it through a commit queue.

> Make DOMWrapperWorld::current() callable from workers
> 
> This CL does the following two things:
> 
> - Makes DOMWrapperWorld::current() callable from workers. Now that a world is always stored in PerContextDataHolder::world(), DOMWrapperWorld::current() can just look up the PerContextDataHolder::world().
> 
> - Makes DOMWrapperWorld::current() callable even when a window object is being initialized. It's possible that some methods call DOMWrapperWorld::current() while the window is being initialized. To handles the subtle situation, this CL adds DOMWrapperWorld::worldOfInitializingWindow.
> 
> 
> BUG=341032
> NOTRY=true
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=168880
> 
> Review URL: https://codereview.chromium.org/182903003

TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/193663005

git-svn-id: svn://svn.chromium.org/blink/trunk@168891 bbb929c8-8fbe-4397-9dbb-9b2b20218538