Convert document item structs to classes

This is the least-complete first run for any of these structs, but this
shift is going to be particularly gnarly, so we need to be
extra-incremental about it.

Change-Id: I7295add8b9a1291f229743f8c36d941569a16ab6
Test: unit tests
Bug: 24410295
Signed-off-by: Casey Dahlin <sadmac@google.com>
diff --git a/generate_java.cpp b/generate_java.cpp
index 3d780d7..d71f8cc 100644
--- a/generate_java.cpp
+++ b/generate_java.cpp
@@ -49,11 +49,11 @@
 
 int
 generate_java(const string& filename, const string& originalSrc,
-                interface_type* iface, JavaTypeNamespace* types)
+                AidlInterface* iface, JavaTypeNamespace* types)
 {
     Class* cl;
 
-    if (iface->document_item.item_type == INTERFACE_TYPE_BINDER) {
+    if (iface->item_type == INTERFACE_TYPE_BINDER) {
         cl = generate_binder_interface_class(iface, types);
     }