Mojom cpp bindings: Enable non-nullable check.

mojo/public/interfaces/bindings/tests/sample_service.mojom

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import "sample_import.mojom"
 import "sample_import2.mojom"
 
 [JavaPackage="org.chromium.mojo.bindings.test.mojom.sample"]
 module sample {
 
@@ skipping 15 matching lines @@
 
 [RequiredFields=7]
 struct Foo {
   const string kFooby = "Fooby";
   string name@8 = kFooby;
   int32 x@0;
   int32 y@1;
   bool a@2 = true;
   bool b@3;
   bool c@4;
-  Bar bar@5;
-  Bar[] extra_bars@7;
-  uint8[] data@6;
-  handle<message_pipe> source@9;
-  handle<data_pipe_consumer>[] input_streams@10;
-  handle<data_pipe_producer>[] output_streams@11;
-  bool[][] array_of_array_of_bools@12;
-  string[][][] multi_array_of_strings@13;
-  bool[] array_of_bools@14;
+  Bar? bar@5;
+  Bar[]? extra_bars@7;
+  uint8[]? data@6;
+  handle<message_pipe>? source@9;
+  handle<data_pipe_consumer>[]? input_streams@10;
+  handle<data_pipe_producer>[]? output_streams@11;
+  bool[][]? array_of_array_of_bools@12;
+  string[][][]? multi_array_of_strings@13;
+  bool[]? array_of_bools@14;
 };
 
 struct DefaultsTest {
   int8 a0@0 = -12;
   uint8 a1@1 = sample.kTwelve;
   int16 a2@2 = 1234;
   uint16 a3@3 = 34567;
   int32 a4@4 = 123456;
   uint32 a5@5 = 3456789012;
   int64 a6@6 = -111111111111;
@@ skipping 34 matching lines @@
   int32 v3 = 3;
 };
 
 [Client=ServiceClient]
 interface Service {
   enum BazOptions {
     REGULAR = 0,
     EXTRA
   };
   const uint8 kFavoriteBaz = 1;
-  Frobinate@0(Foo foo@0, BazOptions baz@1, Port port@2);
+  Frobinate@0(Foo? foo@0, BazOptions baz@1, Port? port@2);
   GetPort@1(Port& port @0);
 };
 
 interface ServiceClient {
   DidFrobinate@0(int32 result@0);
 };
 
 // This interface is referenced above where it is defined. It also refers to
 // itself from a method.
 interface Port {
   PostMessage@0(string message_text@0, Port port@1);
 };
 
 }