Rename and improve "traceable" templates.

third_party/WebKit/Source/platform/heap/Member.h

 // Copyright 2016 The Chromium 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 Member_h
 #define Member_h
 
 #include "wtf/Allocator.h"
 #include "wtf/HashFunctions.h"
 
@@ skipping 293 matching lines @@
     using Hash = WeakMemberHash<T>;
 };
 
 template <typename T>
 struct DefaultHash<blink::UntracedMember<T>> {
     STATIC_ONLY(DefaultHash);
     using Hash = UntracedMemberHash<T>;
 };
 
 template<typename T>
-struct NeedsTracing<blink::Member<T>> {
-    STATIC_ONLY(NeedsTracing);
+struct IsTraceable<blink::Member<T>> {
+    STATIC_ONLY(IsTraceable);
     static const bool value = true;
 };
 
 template<typename T>
 struct IsWeak<blink::WeakMember<T>> {
     STATIC_ONLY(IsWeak);
     static const bool value = true;
 };
 
+template<typename T>
+struct IsTraceable<blink::WeakMember<T>> {
+    STATIC_ONLY(IsTraceable);
+    static const bool value = true;
+};
+
 } // namespace WTF
 
 #endif // Member_h