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

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196637

[haraken, 2015-06-07 23:53:35]

Committed patchset #1 (id:1) manually as r196637.