Implement flag and source getters on RegExp.prototype.

src/messages.h

Index: src/messages.h
diff --git a/src/messages.h b/src/messages.h
index 9e5172c49fd96e2a3ba3fecc79b8226c7b0ba1fc..6d3f797822d4967cb033818d281b5c8aeee54df4 100644
--- a/src/messages.h
+++ b/src/messages.h
@@ -117,8 +117,6 @@ class CallSite {
     "Class extends value % is not a function or null")                         \
   T(FirstArgumentNotRegExp,                                                    \
     "First argument to % must not be a regular expression")                    \
-  T(FlagsGetterNonObject,                                                      \
-    "RegExp.prototype.flags getter called on non-object %")                    \
   T(FunctionBind, "Bind must be called on a function")                         \
   T(GeneratorRunning, "Generator is already running")                          \
   T(IllegalInvocation, "Illegal invocation")                                   \
@@ -203,6 +201,8 @@ class CallSite {
   T(ReduceNoInitial, "Reduce of empty array with no initial value")            \
   T(RegExpFlags,                                                               \
     "Cannot supply flags when constructing one RegExp from another")           \
+  T(RegExpNonObject, "% getter called on non-object %")                        \
+  T(RegExpNonRegExp, "% getter called on non-RegExp object")                   \
   T(ReinitializeIntl, "Trying to re-initialize % object.")                     \
   T(ResolvedOptionsCalledOnNonObject,                                          \
     "resolvedOptions method called on a non-object or on a object that is "    \