Rationalize AddAwakable...() and RemoveAwakable...() methods.

mojo/edk/system/message_pipe.h

Index: mojo/edk/system/message_pipe.h
diff --git a/mojo/edk/system/message_pipe.h b/mojo/edk/system/message_pipe.h
index c5a684dde92028284ba71b15671d97dc818e3842..547d83af9388cf6b607ffd1d0441e681122b116f 100644
--- a/mojo/edk/system/message_pipe.h
+++ b/mojo/edk/system/message_pipe.h
@@ -101,17 +101,15 @@ class MessagePipe final : public ChannelEndpointClient {
   HandleSignalsState GetHandleSignalsState(unsigned port) const;
   MojoResult AddAwakable(unsigned port,
                          Awakable* awakable,
-                         MojoHandleSignals signals,
-                         bool force,
                          uint64_t context,
+                         bool force,
+                         MojoHandleSignals signals,
                          HandleSignalsState* signals_state);
   void RemoveAwakable(unsigned port,
+                      bool match_context,
                       Awakable* awakable,
+                      uint64_t context,
                       HandleSignalsState* signals_state);
-  void RemoveAwakableWithContext(unsigned port,
-                                 Awakable* awakable,
-                                 uint64_t context,
-                                 HandleSignalsState* signals_state);
   void StartSerialize(unsigned port,
                       Channel* channel,
                       size_t* max_size,