Oilpan: Prepare to support garbage-collected Node in WebNode hierarchy.

public/platform/WebPrivatePtr.h

Index: public/platform/WebPrivatePtr.h
diff --git a/public/platform/WebPrivatePtr.h b/public/platform/WebPrivatePtr.h
index cc718fed7fcaea68a7f9acd2d386eef699c9aa52..0d66cb4610fbd34e2eaf1c933de3552f5cd4e67c 100644
--- a/public/platform/WebPrivatePtr.h
+++ b/public/platform/WebPrivatePtr.h
@@ -53,19 +53,10 @@ enum LifetimeManagementType {
 
 template<typename T>
 class LifetimeOf {
-    typedef char TreeSharedType;
-    typedef struct {
-        char padding[8];
-    } NotTreeSharedType;
-
-    template<typename U> static TreeSharedType checkTreeShared(WebCore::TreeShared<U>*);
-    static NotTreeSharedType checkTreeShared(...);
-
     static const bool isGarbageCollected = WTF::IsSubclassOfTemplate<T, WebCore::GarbageCollected>::value;
     static const bool isRefCountedGarbageCollected = WTF::IsSubclassOfTemplate<T, WebCore::RefCountedGarbageCollected>::value;
 public:
     static const LifetimeManagementType value =
-        sizeof(checkTreeShared(static_cast<T*>(0))) == sizeof(TreeSharedType) ? RefCountedLifetime :
         !isGarbageCollected ? RefCountedLifetime :
         isRefCountedGarbageCollected ? RefCountedGarbageCollectedLifetime : GarbageCollectedLifetime;
 };