[es6] Map/Set size getter should have "get size" name

src/runtime/runtime-function.cc

Index: src/runtime/runtime-function.cc
diff --git a/src/runtime/runtime-function.cc b/src/runtime/runtime-function.cc
index c211e1895f742408281a18f4de7db6b77bcdd202..041c8af8df3a4251272633ac268b79608b7cd334 100644
--- a/src/runtime/runtime-function.cc
+++ b/src/runtime/runtime-function.cc
@@ -79,7 +79,7 @@ static Handle<String> NameToFunctionName(Handle<Name> name) {
       stringName = Handle<String>::cast(description);
     }
   } else {
-    stringName = Handle<String>::cast(name);
+    stringName = String::Flatten(Handle<String>::cast(name));
   }
 
   return stringName;