Add a collection implementation.

Change-Id: I47330dc14dd2ecee052b6a5165c6d48bd6c89dc4
diff --git a/src/mark_stack.h b/src/mark_stack.h
index a3e19e9..6b71c84 100644
--- a/src/mark_stack.h
+++ b/src/mark_stack.h
@@ -13,7 +13,7 @@
 
 class MarkStack {
  public:
-  MarkStack* Create(size_t maximum_size);
+  static MarkStack* Create(size_t maximum_size);
 
   ~MarkStack();