Support custom message filtering on Mojo binding objects

mojo/public/cpp/bindings/binding.h

Index: mojo/public/cpp/bindings/binding.h
diff --git a/mojo/public/cpp/bindings/binding.h b/mojo/public/cpp/bindings/binding.h
index 8c9ee2f0c5292c9eaa0d5f534cc3352d0eed9aee..ab1cab30819778c9f40266dc76f95a5d398e2c8b 100644
--- a/mojo/public/cpp/bindings/binding.h
+++ b/mojo/public/cpp/bindings/binding.h
@@ -21,6 +21,7 @@
 namespace mojo {
 
 class AssociatedGroup;
+class MessageReceiver;
 
 // Represents the binding of an interface implementation to a message pipe.
 // When the |Binding| object is destroyed, the binding between the message pipe
@@ -152,6 +153,14 @@ class Binding {
     Bind(request.PassMessagePipe(), std::move(runner));
   }
 
+  // Adds a message filter to be notified of each incoming message before
+  // dispatch. If a filter returns |false| from Accept(), the message is not
+  // dispatched and the pipe is closed. Filters cannot be removed.
+  void AddFilter(std::unique_ptr<MessageReceiver> filter) {
+    DCHECK(is_bound());
+    internal_state_.AddFilter(std::move(filter));
+  }
+
   // Whether there are any associated interfaces running on the pipe currently.
   bool HasAssociatedInterfaces() const {
     return internal_state_.HasAssociatedInterfaces();