components: Make user_prefs a source_set.

components/user_prefs/user_prefs_export.h

Index: components/user_prefs/user_prefs_export.h
diff --git a/components/user_prefs/user_prefs_export.h b/components/user_prefs/user_prefs_export.h
deleted file mode 100644
index af7c0f9041737fa6ee543aaa73f213fc96d01761..0000000000000000000000000000000000000000
--- a/components/user_prefs/user_prefs_export.h
+++ /dev/null
@@ -1,29 +0,0 @@
-// Copyright 2013 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 COMPONENTS_USER_PREFS_USER_PREFS_EXPORT_H_
-#define COMPONENTS_USER_PREFS_USER_PREFS_EXPORT_H_
-
-#if defined(COMPONENT_BUILD)
-#if defined(WIN32)
-
-#if defined(USER_PREFS_IMPLEMENTATION)
-#define USER_PREFS_EXPORT __declspec(dllexport)
-#else
-#define USER_PREFS_EXPORT __declspec(dllimport)
-#endif  // defined(USER_PREFS_IMPLEMENTATION)
-
-#else  // defined(WIN32)
-#if defined(USER_PREFS_IMPLEMENTATION)
-#define USER_PREFS_EXPORT __attribute__((visibility("default")))
-#else
-#define USER_PREFS_EXPORT
-#endif
-#endif
-
-#else  // defined(COMPONENT_BUILD)
-#define USER_PREFS_EXPORT
-#endif
-
-#endif  // COMPONENTS_USER_PREFS_USER_PREFS_EXPORT_H_