Split ExtensionSystem interface from ExtensionSystemImpl implementation, part 1.

extensions/browser/extension_system.cc

Index: extensions/browser/extension_system.cc
diff --git a/extensions/browser/extension_system.cc b/extensions/browser/extension_system.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5038dcbc0eb02158ef9b58ef9a76e6cb97a68334
--- /dev/null
+++ b/extensions/browser/extension_system.cc
@@ -0,0 +1,22 @@
+// 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.
+
+#include "extensions/browser/extension_system.h"
+
+#include "chrome/browser/extensions/extension_system_factory.h"
+
+namespace extensions {
+
+ExtensionSystem::ExtensionSystem() {
+}
+
+ExtensionSystem::~ExtensionSystem() {
+}
+
+// static
+ExtensionSystem* ExtensionSystem::Get(content::BrowserContext* context) {
+  return ExtensionSystemFactory::GetForBrowserContext(context);
+}
+
+}  // namespace extensions