Don't allocate AstTyper with the zone allocator.

src/typing.h

Index: src/typing.h
diff --git a/src/typing.h b/src/typing.h
index f3ead18f99646fa79febb4e5de88db5413e02daf..ccfb973437faa6f672ac1f1f0ffb29f895aa7516 100644
--- a/src/typing.h
+++ b/src/typing.h
@@ -19,17 +19,12 @@ namespace internal {
 
 class AstTyper: public AstVisitor {
  public:
-  static void Run(CompilationInfo* info);
-
-  void* operator new(size_t size, Zone* zone) { return zone->New(size); }
-  void operator delete(void* pointer, Zone* zone) { }
-  void operator delete(void* pointer) { }
+  explicit AstTyper(CompilationInfo* info);
+  void Run();
 
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
 
  private:
-  explicit AstTyper(CompilationInfo* info);
-
   Effect ObservedOnStack(Object* value);
   void ObserveTypesAtOsrEntry(IterationStatement* stmt);