Templatize AstVisitor with its subclass

src/asmjs/typing-asm.h

Index: src/asmjs/typing-asm.h
diff --git a/src/asmjs/typing-asm.h b/src/asmjs/typing-asm.h
index 683f5b2831512ba01c30e1d16b7bc2eee7b9d985..78ccb7c945ff9f293041fba63124760878b5c8fa 100644
--- a/src/asmjs/typing-asm.h
+++ b/src/asmjs/typing-asm.h
@@ -18,7 +18,7 @@ namespace internal {
 
 class TypeCache;
 
-class AsmTyper : public AstVisitor {
+class AsmTyper final : public AstVisitor<AsmTyper> {
  public:
   explicit AsmTyper(Isolate* isolate, Zone* zone, Script* script,
                     FunctionLiteral* root);
@@ -132,8 +132,8 @@ class AsmTyper : public AstVisitor {
   void InitializeStdlib();
   void InitializeStdlibSIMD();
 
-  void VisitDeclarations(ZoneList<Declaration*>* d) override;
-  void VisitStatements(ZoneList<Statement*>* s) override;
+  void VisitDeclarations(ZoneList<Declaration*>* d);
+  void VisitStatements(ZoneList<Statement*>* s);
 
   void VisitExpressionAnnotation(Expression* e, Variable* var, bool is_return);
   void VisitFunctionAnnotation(FunctionLiteral* f);
@@ -178,7 +178,7 @@ class AsmTyper : public AstVisitor {
 
   Zone* zone() const { return zone_; }
 
-#define DECLARE_VISIT(type) void Visit##type(type* node) override;
+#define DECLARE_VISIT(type) void Visit##type(type* node);
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT