Remove obviously unneeded forward declarations from headers under src/{app,base,net}.

base/file_version_info_win.h

Index: base/file_version_info_win.h
diff --git a/base/file_version_info_win.h b/base/file_version_info_win.h
index c2bde7735b9e980061e6f86c9b015466903495fd..3d60d69ef19b37f87cab1f84ac26e7ab4c317963 100644
--- a/base/file_version_info_win.h
+++ b/base/file_version_info_win.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2006-2008 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.
 
@@ -15,8 +15,6 @@
 struct tagVS_FIXEDFILEINFO;
 typedef tagVS_FIXEDFILEINFO VS_FIXEDFILEINFO;
 
-class FilePath;
-
 // Provides a way to access the version information for a file.
 // This is the information you access when you select a file in the Windows
 // explorer, right-click select Properties, then click the Version tab.