Implement flag and source getters on RegExp.prototype.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 127daddb074f6fa64304f2123501610aee978508..a3f533bc52d85c3b676aad65adfadbbbdcaac0b1 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -7812,11 +7812,9 @@ class JSRegExp: public JSObject {
 
   // In-object fields.
   static const int kSourceFieldIndex = 0;
-  static const int kGlobalFieldIndex = 1;
-  static const int kIgnoreCaseFieldIndex = 2;
-  static const int kMultilineFieldIndex = 3;
-  static const int kLastIndexFieldIndex = 4;
-  static const int kInObjectFieldCount = 5;
+  static const int kFlagsFieldIndex = 1;
+  static const int kLastIndexFieldIndex = 2;
+  static const int kInObjectFieldCount = 3;
 
   // The uninitialized value for a regexp code object.
   static const int kUninitializedValue = -1;