Add Type::cast

R=danno@chromium.org
BUG=

Review URL: https://codereview.chromium.org/18843002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15551 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects.cc

@@ -15850,8 +15850,8 @@ MaybeObject* PropertyCell::SetValueInferType(Object* value,
         &PropertyCell::UpdateType,
         Handle<PropertyCell>(this),
         Handle<Object>(value, GetIsolate()));
-    if (maybe_type->IsFailure()) return maybe_type;
-    Type* new_type = static_cast<Type*>(maybe_type);
+    Type* new_type;
+    if (maybe_type->To(&new_type)) return maybe_type;
     set_type(new_type);
   }
   return value;

src/types.h

@@ -184,6 +184,13 @@ class Type : public Object {
     return Iterator<v8::internal::Object>(this->handle());
   }
 
+  static Type* cast(v8::internal::Object* object) {
+    Type* t = static_cast<Type*>(object);
+    ASSERT(t->is_bitset() || t->is_class() ||
+           t->is_constant() || t->is_union());
+    return t;
+  }
+
  private:
   // A union is a fixed array containing types. Invariants:
   // - its length is at least 2