Revert 196501 "Oilpan: Make PersistentNode hold a raw pointer"
Revert 196501 "Oilpan: Make PersistentNode hold a raw pointer"

Discussed offline, and realized that this step is not helpful to remove
m_trace from PersistentNode.

> Oilpan: Make PersistentNode hold a raw pointer
> 
> This CL changes:
> 
>   class PersistentNode { };
>   class PersistentBase : public PersistentNode { };
>   class Persistent {
>     T* m_raw;
>   };
>   class CrossThreadPersistent {
>     T* m_raw;
>   };
> 
> to:
> 
>   class PersistentNode {
>     void* m_raw;
>   };
>   class PersistentBase : public PersistentNode { };
>   class Persistent { };
>   class CrossThreadPersistent { };
> 
> This is a preparation for tracing the m_raw from PersistentNode and thus
> remove PersistentNode::m_trace in a follow-up CL.
> 
> BUG=483380
> 
> Review URL: https://codereview.chromium.org/1159003006

TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/1157203004

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@196637 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk