Add support for attaching filters to an IPC TestSink.

ipc/ipc_test_sink.cc

Index: ipc/ipc_test_sink.cc
diff --git a/ipc/ipc_test_sink.cc b/ipc/ipc_test_sink.cc
index 95900b6ca5074a164b45491431ffc7e86e5e9b66..44042390727c75455a5758e16cb55c1be521610a 100644
--- a/ipc/ipc_test_sink.cc
+++ b/ipc/ipc_test_sink.cc
@@ -21,6 +21,14 @@ bool TestSink::Send(Message* message) {
 }
 
 bool TestSink::OnMessageReceived(const Message& msg) {
+  ObserverListBase<Channel::Listener>::Iterator it(filter_list_);
+  Channel::Listener* observer;
+  while ((observer = it.GetNext()) != NULL) {
+    if (observer->OnMessageReceived(msg))
+      return true;
+  }
+
+  // No filter handled the message, so store it.
   messages_.push_back(Message(msg));
   return true;
 }
@@ -57,4 +65,12 @@ const Message* TestSink::GetUniqueMessageMatching(uint32 id) const {
   return &messages_[found_index];
 }
 
+void TestSink::AddFilter(Channel::Listener* filter) {
+  filter_list_.AddObserver(filter);
+}
+
+void TestSink::RemoveFilter(Channel::Listener* filter) {
+  filter_list_.RemoveObserver(filter);
+}
+
 }  // namespace IPC