Add validation test cases for struct versioning.

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

Index: mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom
diff --git a/mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom b/mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom
index fb1f4b7f2016e9f07d9faefc599ba95afe1d145e..13d0b528127f85375e8b523b690bb62f2f8dc8ef 100644
--- a/mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom
+++ b/mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom
@@ -31,6 +31,16 @@ struct StructF {
   array<uint8, 3> fixed_size_array;
 };
 
+struct StructG {
+  int32 i;
+  [MinVersion=1]
+  StructA? struct_a;
+  [MinVersion=3]
+  string? str;
+  [MinVersion=3]
+  bool b;
+};
+
 interface ConformanceTestInterface {
   Method0(float param0);
   Method1(StructA param0);
@@ -43,6 +53,7 @@ interface ConformanceTestInterface {
   Method8(array<array<string>?> param0);
   Method9(array<array<handle?>>? param0);
   Method10(map<string, uint8> param0);
+  Method11(StructG param0);
 };
 
 struct BasicStruct {