Support [handles] in validation test input format and add handle-related tests.

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 d8d66c36be9685751c235fc4b9b27004033ffdbc..c16c384c87d0ca8548e96c43686d217daf01b988 100644
--- a/mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom
+++ b/mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom
@@ -16,12 +16,22 @@ struct StructC {
   uint8[] array;
 };
 
+struct StructD {
+  handle<message_pipe>[] message_pipes;
+};
+
+struct StructE {
+  StructD struct_d;
+  handle<data_pipe_consumer> data_pipe_consumer;
+};
+
 interface ConformanceTestInterface {
   Method0(float param0);
   Method1(StructA param0);
   Method2(StructB param0, StructA param1);
   Method3(bool[] param0);
   Method4(StructC param0, uint8[] param1);
+  Method5(StructE param0, handle<data_pipe_producer> param1);
 };
 
 struct BasicStruct {