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

chrome/browser/extensions/extension_devtools_bridge.h

Index: chrome/browser/extensions/extension_devtools_bridge.h
diff --git a/chrome/browser/extensions/extension_devtools_bridge.h b/chrome/browser/extensions/extension_devtools_bridge.h
index b9b8385980d02a0b0e06ed3539683f68db7e995c..ad103a272b1ab5ed81d8a9fdb0a9d60989d00e6f 100644
--- a/chrome/browser/extensions/extension_devtools_bridge.h
+++ b/chrome/browser/extensions/extension_devtools_bridge.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.
 
@@ -14,7 +14,6 @@
 #include "chrome/browser/extensions/extension_message_service.h"
 
 class Profile;
-struct DevToolsMessageData;
 
 // This class is a DevToolsClientHost that fires extension events.
 class ExtensionDevToolsBridge : public DevToolsClientHost {