Reland "Use V8_FINAL and V8_OVERRIDE in various places, fixing bugs revealed by them.".

src/ast.cc

Index: src/ast.cc
diff --git a/src/ast.cc b/src/ast.cc
index 23b680d47f4805dbb2b18a7a4cf3f8c82c6bb485..8f69bd705923b7e9136d3881ebffca5f4507d9e8 100644
--- a/src/ast.cc
+++ b/src/ast.cc
@@ -858,12 +858,13 @@ bool RegExpCapture::IsAnchoredAtEnd() {
 // in as many cases as possible, to make it more difficult for incorrect
 // parses to look as correct ones which is likely if the input and
 // output formats are alike.
-class RegExpUnparser: public RegExpVisitor {
+class RegExpUnparser V8_FINAL : public RegExpVisitor {
  public:
   explicit RegExpUnparser(Zone* zone);
   void VisitCharacterRange(CharacterRange that);
   SmartArrayPointer<const char> ToString() { return stream_.ToCString(); }
-#define MAKE_CASE(Name) virtual void* Visit##Name(RegExp##Name*, void* data);
+#define MAKE_CASE(Name) virtual void* Visit##Name(RegExp##Name*,          \
+                                                  void* data) V8_OVERRIDE;
   FOR_EACH_REG_EXP_TREE_TYPE(MAKE_CASE)
 #undef MAKE_CASE
  private: