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

mojo/edk/system/awakable_list.h

 // 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.
 
 #ifndef MOJO_EDK_SYSTEM_AWAKABLE_LIST_H_
 #define MOJO_EDK_SYSTEM_AWAKABLE_LIST_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 16 matching lines @@
 // be protected by some lock).
 class AwakableList {
  public:
   AwakableList();
   ~AwakableList();
 
   void AwakeForStateChange(const HandleSignalsState& state);
   void CancelAll();
   void Add(Awakable* awakable, MojoHandleSignals signals, uint64_t context);
   void Remove(Awakable* awakable);
+  void RemoveWithContext(Awakable* awakable, uint64_t context);
 
  private:
   struct AwakeInfo {
     AwakeInfo(Awakable* awakable, MojoHandleSignals signals, uint64_t context)
         : awakable(awakable), signals(signals), context(context) {}
 
     Awakable* awakable;
     MojoHandleSignals signals;
     uint64_t context;
   };
   using AwakeInfoList = std::vector<AwakeInfo>;
 
   AwakeInfoList awakables_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(AwakableList);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_AWAKABLE_LIST_H_