Mojom: Add 'default' keyword for initializing structs to non-null value.

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.sample"]
 module sample {
 
@@ skipping 32 matching lines @@
 };
 
 struct DefaultsTest {
   int8 a0@0 = -12;
   uint8 a1@1 = sample.kTwelve;
   int16 a2@2 = 1234;
   uint16 a3@3 = 34567;
   int32 a4@4 = 123456;
   // TODO(vtl): crbug.com/375522
   uint32 a5@5 /* = 3456789012 */;
+  int64 a6@6 = 111111111111;
   // TODO(vtl): crbug.com/375522
-  int64 a6@6 = 111111111111;
   uint64 a7@7 /* = 9999999999999999999 */;
   int32 a8@8 = 0x12345;
   int32 a9@9 = -0x12345;
   int32 a10@10 = +1234;
   bool a11@11 = true;
   bool a12@12 = false;
   float a13@13 = 123.25;
   double a14@14 = 1234567890.123;
   double a15@15 = 1E10;
   double a16@16 = -1.2E+20;
   double a17@17 = +1.23E-20;
 
   // TODO(vtl): Add tests for default vs null when those are implemented (for
   // structs, arrays, and strings).
   uint8[] a18@18;
   string a19@19;
 
   Bar.Type a20@20 = Bar.TYPE_BOTH;
   imported.Point a21@21;
-  imported.Thing a22@22;
+  imported.Thing a22@22 = default;
 };
 
 struct StructWithHoleV1 {
   int32 v1 = 1;
   int64 v2 = 2;
 };
 
 struct StructWithHoleV2 {
   int32 v1 = 1;
   int64 v2 = 2;
@@ skipping 15 matching lines @@
   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);
 };
 
 }