Eliminate recursion in ZoneSplayTree traversal.

src/zone.h

Index: src/zone.h
diff --git a/src/zone.h b/src/zone.h
index cdbab3282130834bd961133fa9fbd312f5e4f65c..4e4f1d7224cdea704f0308cc0f2c6fc053c6861b 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -204,10 +204,6 @@ class ZoneScope BASE_EMBEDDED {
 };
 
 
-template <typename Node, class Callback>
-static void DoForEach(Node* node, Callback* callback);
-
-
 // A zone splay tree.  The config type parameter encapsulates the
 // different configurations of a concrete splay tree:
 //
@@ -297,9 +293,7 @@ class ZoneSplayTree : public ZoneObject {
   };
 
   template <class Callback>
-  void ForEach(Callback* c) {
-    DoForEach<typename ZoneSplayTree<Config>::Node, Callback>(root_, c);
-  }
+  void ForEach(Callback* callback);
 
  private:
   Node* root_;