components: Extract pref_registry component out of user_prefs.

components/pref_registry/pref_registry_export.h

Index: components/pref_registry/pref_registry_export.h
diff --git a/components/pref_registry/pref_registry_export.h b/components/pref_registry/pref_registry_export.h
new file mode 100644
index 0000000000000000000000000000000000000000..9ebbb1fea0ddef134ee1a7b8a4d6063848a5f2f1
--- /dev/null
+++ b/components/pref_registry/pref_registry_export.h
@@ -0,0 +1,29 @@
+// Copyright 2014 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_PREF_REGISTRY_PREF_REGISTRY_EXPORT_H_
+#define COMPONENTS_PREF_REGISTRY_PREF_REGISTRY_EXPORT_H_
+
+#if defined(COMPONENT_BUILD)
+#if defined(WIN32)
+
+#if defined(PREF_REGISTRY_IMPLEMENTATION)
+#define PREF_REGISTRY_EXPORT __declspec(dllexport)
+#else
+#define PREF_REGISTRY_EXPORT __declspec(dllimport)
+#endif  // defined(PREF_REGISTRY_IMPLEMENTATION)
+
+#else  // defined(WIN32)
+#if defined(PREF_REGISTRY_IMPLEMENTATION)
+#define PREF_REGISTRY_EXPORT __attribute__((visibility("default")))
+#else
+#define PREF_REGISTRY_EXPORT
+#endif
+#endif
+
+#else  // defined(COMPONENT_BUILD)
+#define PREF_REGISTRY_EXPORT
+#endif
+
+#endif  // COMPONENTS_PREF_REGISTRY_PREF_REGISTRY_EXPORT_H_