Support COM in SequencedWorkerPool. This will be used by some code that

base/win/scoped_com_initializer.h

 // Copyright (c) 2012 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 BASE_WIN_SCOPED_COM_INITIALIZER_H_
 #define BASE_WIN_SCOPED_COM_INITIALIZER_H_
 
 #include <objbase.h>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "build/build_config.h"
 
 namespace base {
 namespace win {
 
 // Initializes COM in the constructor (STA or MTA), and uninitializes COM in the
 // destructor.
+//
+// WARNING: This should only be used once per thread, ideally scoped to a
+// similar lifetime as the thread itself.  You should not be using this in
+// random utility functions that make COM calls -- instead ensure these
+// functions are running on a COM-supporting thread!
 class ScopedCOMInitializer {
  public:
   // Enum value provided to initialize the thread as an MTA instead of STA.
   enum SelectMTA { kMTA };
 
   // Constructor for STA initialization.
   ScopedCOMInitializer() {
     Initialize(COINIT_APARTMENTTHREADED);
   }
 
@@ skipping 36 matching lines @@
   DWORD thread_id_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ScopedCOMInitializer);
 };
 
 }  // namespace win
 }  // namespace base
 
 #endif  // BASE_WIN_SCOPED_COM_INITIALIZER_H_