Make it possible to remove an Awakable with a specific "context" from a Dispatcher.

mojo/edk/system/data_pipe_producer_dispatcher.cc

Index: mojo/edk/system/data_pipe_producer_dispatcher.cc
diff --git a/mojo/edk/system/data_pipe_producer_dispatcher.cc b/mojo/edk/system/data_pipe_producer_dispatcher.cc
index 829c71d6a864a0fdf06da8ab16c7155908b996d3..c9c686a140fa3e7bdb2d9e83829bcd37493ec881 100644
--- a/mojo/edk/system/data_pipe_producer_dispatcher.cc
+++ b/mojo/edk/system/data_pipe_producer_dispatcher.cc
@@ -185,6 +185,15 @@ void DataPipeProducerDispatcher::RemoveAwakableImplNoLock(
   data_pipe_->ProducerRemoveAwakable(awakable, signals_state);
 }
 
+void DataPipeProducerDispatcher::RemoveAwakableWithContextImplNoLock(
+    Awakable* awakable,
+    uint64_t context,
+    HandleSignalsState* signals_state) {
+  mutex().AssertHeld();
+  data_pipe_->ProducerRemoveAwakableWithContext(awakable, context,
+                                                signals_state);
+}
+
 void DataPipeProducerDispatcher::StartSerializeImplNoLock(
     Channel* channel,
     size_t* max_size,