[runtime] First step to sanitize regexp literal creation.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 42a1c7e317863d57cf3f406e3ad099ec44793053..707ace30cac4b67a04843afa564361de485ff8f7 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -15666,6 +15666,13 @@ MaybeHandle<JSRegExp> JSRegExp::New(Handle<String> pattern,
 }
 
 
+// static
+Handle<JSRegExp> JSRegExp::Copy(Handle<JSRegExp> regexp) {
+  Isolate* const isolate = regexp->GetIsolate();
+  return Handle<JSRegExp>::cast(isolate->factory()->CopyJSObject(regexp));
+}
+
+
 static JSRegExp::Flags RegExpFlagsFromString(Handle<String> flags,
                                              bool* success) {
   uint32_t value = JSRegExp::NONE;