[mojo] Add mojom parser support for native-only structs

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

Index: mojo/public/interfaces/bindings/tests/test_native_types.mojom
diff --git a/mojo/public/interfaces/bindings/tests/scoping.mojom b/mojo/public/interfaces/bindings/tests/test_native_types.mojom
similarity index 63%
copy from mojo/public/interfaces/bindings/tests/scoping.mojom
copy to mojo/public/interfaces/bindings/tests/test_native_types.mojom
index 2e9edb10b4eddfca591bdf64966238b9a75fbe2f..3537703ec9a054343d0af35b6526a070291f7cc9 100644
--- a/mojo/public/interfaces/bindings/tests/scoping.mojom
+++ b/mojo/public/interfaces/bindings/tests/test_native_types.mojom
@@ -4,14 +4,8 @@
 
 module mojo.test;
 
-interface A {
-  GetB(B& b);
-};
+// Used to verify that structs can be declared with no body in mojom.
 
-interface B {
-  GetC(C& c);
-};
+[native=True]
+struct PickledStruct;
 
-interface C {
-  D();
-};