EDK: Add handle rights checking to the various entrypoints.

mojo/edk/system/entrypoint_class.h

Index: mojo/edk/system/entrypoint_class.h
diff --git a/mojo/edk/system/entrypoint_class.h b/mojo/edk/system/entrypoint_class.h
index 05c172b77028e8c068e30dea0d2e4b4c3f934a12..d6828a96fdb7fcaa11cb76d17c58c69222da2497 100644
--- a/mojo/edk/system/entrypoint_class.h
+++ b/mojo/edk/system/entrypoint_class.h
@@ -15,6 +15,10 @@ namespace system {
 // |SupportsEntrypointClass()| indicates that the method's class is not
 // supported.
 enum class EntrypointClass {
+  // Not an entrypoint; all implementations of
+  // |Dispatcher::SupportsEntrypointClass()| should return true for this:
+  NONE,
+
   // |Dispatcher::ReadMessage()|, |Dispatcher::WriteMessage()|:
   MESSAGE_PIPE,