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

chrome/browser/extensions/extension_devtools_browsertest.h

Index: chrome/browser/extensions/extension_devtools_browsertest.h
diff --git a/chrome/browser/extensions/extension_devtools_browsertest.h b/chrome/browser/extensions/extension_devtools_browsertest.h
index 5313abfd4d983687c4e625594ea0f4801d2fba8a..1f7c3ee2522309a6660e07b2a71a1730b8936001 100644
--- a/chrome/browser/extensions/extension_devtools_browsertest.h
+++ b/chrome/browser/extensions/extension_devtools_browsertest.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.
 
@@ -6,9 +6,10 @@
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_DEVTOOLS_BROWSERTEST_H_
 #pragma once
 
-#include "base/command_line.h"
 #include "chrome/browser/extensions/extension_browsertest.h"
 
+class CommandLine;
+
 // Subclass of ExtensionBrowserTest that enables the devtools
 // command line features.
 class ExtensionDevToolsBrowserTest : public ExtensionBrowserTest {