Support custom message filtering on Mojo binding objects

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

Index: mojo/public/cpp/bindings/lib/message.cc
diff --git a/mojo/public/cpp/bindings/lib/message.cc b/mojo/public/cpp/bindings/lib/message.cc
index d99ced3d28f0acaf03df2eb806574f2f549d5e08..0018a03bcd7909b9b9657f5d66b6c750b1941485 100644
--- a/mojo/public/cpp/bindings/lib/message.cc
+++ b/mojo/public/cpp/bindings/lib/message.cc
@@ -114,6 +114,12 @@ void Message::CloseHandles() {
   }
 }
 
+PassThroughFilter::PassThroughFilter() {}
+
+PassThroughFilter::~PassThroughFilter() {}
+
+bool PassThroughFilter::Accept(Message* message) { return true; }
+
 SyncMessageResponseContext::SyncMessageResponseContext()
     : outer_context_(current()) {
   g_tls_sync_response_context.Get().Set(this);