Revert 167313 "We've replaced SharedPersistent with ScopedPersis..."

This is a speculative revert to fix failures in interactive_tests in windows.
http://build.chromium.org/p/chromium.webkit/builders/Win7%20%28dbg%29/builds/13518


> We've replaced SharedPersistent with ScopedPersistent or ScriptValue before, but a couple of SharedPersistents are remaining. So this CL replaces them.
> 
> Ideally we want to remove SharedPersistent though.
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=165751
> 
> Review URL: https://codereview.chromium.org/146523002

TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/171233009

git-svn-id: svn://svn.chromium.org/blink/trunk@167448 bbb929c8-8fbe-4397-9dbb-9b2b20218538