Support custom message filtering on Mojo binding objects

mojo/public/cpp/bindings/binding.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_BINDING_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_BINDING_H_
 
 #include <utility>
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "mojo/public/cpp/bindings/interface_ptr.h"
 #include "mojo/public/cpp/bindings/interface_ptr_info.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/cpp/bindings/lib/binding_state.h"
 #include "mojo/public/cpp/system/core.h"
 
 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
 // and the interface is torn down and the message pipe is closed, leaving the
 // interface implementation in an unbound state.
 //
 // Example:
 //
 //   #include "foo.mojom.h"
 //
@@ skipping 111 matching lines @@
 
   // Completes a binding that was constructed with only an interface
   // implementation by removing the message pipe endpoint from |request| and
   // binding it to the previously specified implementation.
   void Bind(InterfaceRequest<Interface> request,
             scoped_refptr<base::SingleThreadTaskRunner> runner =
                 base::ThreadTaskRunnerHandle::Get()) {
     Bind(request.PassMessagePipe(), std::move(runner));
   }
 
+  // Adds a message filter to be notified of each incoming message and
+  // optionally prevent it from being dispatched. Filters cannot be removed.

[yzshen1, 2016/08/24 20:47:55]

Returning false not just prevents the message from being dispatched, but also
disconnects the pipe.

(I think that behavior is fine for now. Please consider updating the comment)

[Ken Rockot(use gerrit already), 2016/08/24 20:56:38]

Done

+  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();
   }
 
   // Stops processing incoming messages until
   // ResumeIncomingMethodCallProcessing(), or WaitForIncomingMethodCall().
   // Outgoing messages are still sent.
   //
   // No errors are detected on the message pipe while paused.
@@ skipping 80 matching lines @@
  private:
   internal::BindingState<Interface, Interface::PassesAssociatedKinds_>
       internal_state_;
 
   DISALLOW_COPY_AND_ASSIGN(Binding);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_BINDING_H_