Enable TypeError for dictionary members of non-nullable interface type

third_party/WebKit/Source/modules/gamepad/GamepadEventInit.idl

Index: third_party/WebKit/Source/modules/gamepad/GamepadEventInit.idl
diff --git a/third_party/WebKit/Source/modules/gamepad/GamepadEventInit.idl b/third_party/WebKit/Source/modules/gamepad/GamepadEventInit.idl
index 4291a7eb051c25753f9363b48f754f897df02ac1..3bccf6c8491721d41762f0785b7d16d7a4407ec3 100644
--- a/third_party/WebKit/Source/modules/gamepad/GamepadEventInit.idl
+++ b/third_party/WebKit/Source/modules/gamepad/GamepadEventInit.idl
@@ -2,8 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// https://dvcs.w3.org/hg/gamepad/raw-file/default/gamepad.html#gamepadevent-interface
+// https://w3c.github.io/gamepad/#gamepadevent-interface
 
 dictionary GamepadEventInit : EventInit {
-    Gamepad gamepad;
+    // TODO(foolip): |gamepad| should be required and not nullable.
+    // https://crbug.com/647693
+    // https://github.com/w3c/gamepad/issues/35
+    Gamepad? gamepad;
 };