[stubs] Properly handle length overflow in StringAddStub.

src/runtime/runtime-internal.cc

Index: src/runtime/runtime-internal.cc
diff --git a/src/runtime/runtime-internal.cc b/src/runtime/runtime-internal.cc
index 6bc27d4bf42e8f9571bcc7c534c7dffb17661bf6..fc689fc4f7411b32ebed6d2650055f8553e831d4 100644
--- a/src/runtime/runtime-internal.cc
+++ b/src/runtime/runtime-internal.cc
@@ -230,6 +230,12 @@ RUNTIME_FUNCTION(Runtime_ThrowIncompatibleMethodReceiver) {
       NewTypeError(MessageTemplate::kIncompatibleMethodReceiver, arg0, arg1));
 }
 
+RUNTIME_FUNCTION(Runtime_ThrowInvalidStringLength) {
+  HandleScope scope(isolate);

[Michael Starzinger, 2016/07/14 11:14:20]

nit: DCHECK_EQ(0, args.length());

[Benedikt Meurer, 2016/07/14 11:22:29]

Doesn't matter.

+  THROW_NEW_ERROR_RETURN_FAILURE(
+      isolate, NewTypeError(MessageTemplate::kInvalidStringLength));
+}
+
 RUNTIME_FUNCTION(Runtime_ThrowIteratorResultNotAnObject) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);