[regexp] quantifier refers to the surrogate pair in unicode regexp.

src/regexp/regexp-parser.h

Index: src/regexp/regexp-parser.h
diff --git a/src/regexp/regexp-parser.h b/src/regexp/regexp-parser.h
index 5ce2bb080ecd83881f63c0f6dca7da5d775b4459..af9b765fba16b0de0f00d814da565a8ebd993ec1 100644
--- a/src/regexp/regexp-parser.h
+++ b/src/regexp/regexp-parser.h
@@ -101,6 +101,7 @@ class RegExpBuilder : public ZoneObject {
  public:
   explicit RegExpBuilder(Zone* zone);
   void AddCharacter(uc16 character);
+  void AddUnicodeCharacter(uc32 character);
   // "Adds" an empty expression. Does nothing except consume a
   // following quantifier
   void AddEmpty();