Mojo: Add NotifyBadMessage API

mojo/public/cpp/bindings/lib/connector.cc

Index: mojo/public/cpp/bindings/lib/connector.cc
diff --git a/mojo/public/cpp/bindings/lib/connector.cc b/mojo/public/cpp/bindings/lib/connector.cc
index 9f1037ceae81b09ef3948d6532b7f1cec9a524ff..eee2d1a9ca626c81c3831007353df375d413874f 100644
--- a/mojo/public/cpp/bindings/lib/connector.cc
+++ b/mojo/public/cpp/bindings/lib/connector.cc
@@ -266,9 +266,10 @@ bool Connector::ReadSingleMessage(MojoResult* read_result) {
   const MojoResult rv = ReadMessage(message_pipe_.get(), &message);
   *read_result = rv;
 
-  if (rv == MOJO_RESULT_OK) {
-    receiver_result =
-        incoming_receiver_ && incoming_receiver_->Accept(&message);
+  if (rv == MOJO_RESULT_OK && incoming_receiver_) {
+    receiver_result = incoming_receiver_->Accept(&message);
+    if (!receiver_result)
+      message.NotifyBadMessage(interface_name_);

[yzshen1, 2016/06/11 00:10:59]

For multiplex router, we may get here because of message header validation
failure. In that case, it can be any associated interface, not necessarily the
master interface. So the interface name is misleading.

Besides, there are places that this CL doesn't report bad messages:
- in multiplex_router.cc, pipe control message validation failure.
- in router.cc, we may delay processing of async messages, although the messages
have passed default validation, it hasn't done custom validation (enforced by
users' StructTraits, etc.) yet. So when the message is actually dispatched, it
may still fail.

One way that may be easier to catch all cases, is to check the result value here
(the synchronous case) plus Connector::RaiseError (the async case). And we don't
need to worry about inserting NotifyBadMessage at high level.

If we go down this direction, we will need to add parameter to RaiseError to
distinguish bad message from other reasons.

[Ken Rockot(use gerrit already), 2016/06/11 21:48:30]

Ah right. It's a bit more complicated than this too because MessageFilters can
reject along the way. Given the additional complexity required to get this right
in the bindings, I've removed all bindings changes from this CL and will send
you a follow-up CL with those changes. Thanks!

   }
 
   if (!weak_self)