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

mojo/edk/system/message_pipe_dispatcher.cc

 // Copyright 2013 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.
 
 #include "mojo/edk/system/message_pipe_dispatcher.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "mojo/edk/system/configuration.h"
@@ skipping 200 matching lines @@
                                     signals_state);
 }
 
 void MessagePipeDispatcher::RemoveAwakableImplNoLock(
     Awakable* awakable,
     HandleSignalsState* signals_state) {
   mutex().AssertHeld();
   message_pipe_->RemoveAwakable(port_, awakable, signals_state);
 }
 
+void MessagePipeDispatcher::RemoveAwakableWithContextImplNoLock(
+    Awakable* awakable,
+    uint64_t context,
+    HandleSignalsState* signals_state) {
+  mutex().AssertHeld();
+  message_pipe_->RemoveAwakableWithContext(port_, awakable, context,
+                                           signals_state);
+}
+
 void MessagePipeDispatcher::StartSerializeImplNoLock(
     Channel* channel,
     size_t* max_size,
     size_t* max_platform_handles) {
   AssertHasOneRef();  // Only one ref => no need to take the lock.
   return message_pipe_->StartSerialize(port_, channel, max_size,
                                        max_platform_handles);
 }
 
 bool MessagePipeDispatcher::EndSerializeAndCloseImplNoLock(
     Channel* channel,
     void* destination,
     size_t* actual_size,
     std::vector<ScopedPlatformHandle>* platform_handles) {
   AssertHasOneRef();  // Only one ref => no need to take the lock.
 
   bool rv = message_pipe_->EndSerialize(port_, channel, destination,
                                         actual_size, platform_handles);
   message_pipe_ = nullptr;
   port_ = kInvalidPort;
   return rv;
 }
 
 }  // namespace system
 }  // namespace mojo