Introduce TypeFeedbackVector, as FixedArray grew constrictive.

src/type-feedback-vector.h

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_TYPE_FEEDBACK_VECTOR_H_
+#define V8_TYPE_FEEDBACK_VECTOR_H_
+
+#include "src/checks.h"
+#include "src/elements-kind.h"
+#include "src/heap/heap.h"
+#include "src/isolate.h"
+#include "src/objects.h"
+
+namespace v8 {
+namespace internal {
+
+class TypeFeedbackVector : public FixedArray {
+ public:
+  // Casting.
+  static TypeFeedbackVector* cast(Object* obj) {
+    DCHECK(obj->IsTypeFeedbackVector());
+    return reinterpret_cast<TypeFeedbackVector*>(obj);
+  }
+
+  static Handle<TypeFeedbackVector> Copy(Isolate* isolate,
+                                         Handle<TypeFeedbackVector> vector);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(TypeFeedbackVector);
+};
+}
+}  // namespace v8::internal
+
+#endif  // V8_TRANSITIONS_H_