[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 67%
copy from mojo/public/interfaces/bindings/tests/scoping.mojom
copy to mojo/public/interfaces/bindings/tests/test_native_types.mojom
index 2e9edb10b4eddfca591bdf64966238b9a75fbe2f..b23d411212741b90b0ad516f64fb00bab4afb975 100644
--- a/mojo/public/interfaces/bindings/tests/scoping.mojom
+++ b/mojo/public/interfaces/bindings/tests/test_native_types.mojom
@@ -4,14 +4,7 @@
 
 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);
-};
+struct PickledStruct;

[yzshen1, 2015/12/14 21:33:10]

This looks like a "forward declaration".

What do you think if we use something more explicit, say:
[native]
struct PickledStruct;

And only allow struct-without-body if attribute [native] is present.

Another thing is whether it is necessary to be a "struct"? From users'
perspective, they can put anything in this blob of memory, right? E.g., simply
an int32 or a vector. From bindings' perspective, maybe the bindings doesn't
have to encode the memory as a mojo struct either.
(But maybe it is okay comparing with introducing a new keyword. :))

 
-interface C {
-  D();
-};