Add field-initializing constructors to generated mojo structs.

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

Index: mojo/public/interfaces/bindings/tests/test_structs.mojom
diff --git a/mojo/public/interfaces/bindings/tests/test_structs.mojom b/mojo/public/interfaces/bindings/tests/test_structs.mojom
index 683f0a56a08fe68fee7ff7b3d901978c97265495..60c4245bc5846ca5d67a2f62d8fd87d05dd1ba66 100644
--- a/mojo/public/interfaces/bindings/tests/test_structs.mojom
+++ b/mojo/public/interfaces/bindings/tests/test_structs.mojom
@@ -360,6 +360,16 @@ struct MultiVersionStructV7 {
   bool f_bool;
 };
 
+// A struct where the fields are not sorted by their ordinals.
+struct ReorderedStruct {
+  [MinVersion=2]
+  int64 f_int64@3 = 3;
+  [MinVersion=4]
+  uint32 f_uint32@6 = 6;
+  [MinVersion=1]
+  int32 f_int32@1 = 1;
+};
+
 // Used to verify that interfaces that are struct members can be defined in the
 // same file.