Remove obviously unneeded forward declarations in chrome/browser/[abef]*/*.h.

chrome/browser/extensions/extension_bookmarks_module.h

Index: chrome/browser/extensions/extension_bookmarks_module.h
diff --git a/chrome/browser/extensions/extension_bookmarks_module.h b/chrome/browser/extensions/extension_bookmarks_module.h
index 3105dfa94bf2e7efabf09269159c4e062569eb59..a2590bcd31ff8f62d51f8cd27ed108b92adbbcd5 100644
--- a/chrome/browser/extensions/extension_bookmarks_module.h
+++ b/chrome/browser/extensions/extension_bookmarks_module.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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.
 
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <list>
+#include <set>
 #include <string>
 
 #include "base/singleton.h"