Move small c/b/extensions classes into extensions namespace no.1

chrome/browser/extensions/app_shortcut_manager.cc

Index: chrome/browser/extensions/app_shortcut_manager.cc
diff --git a/chrome/browser/extensions/app_shortcut_manager.cc b/chrome/browser/extensions/app_shortcut_manager.cc
index 6d8fc81656d41ba09b50568b643fabf5760c487d..e75a5db4307c7eb0ca69b45a0faeb8a0d1199d9f 100644
--- a/chrome/browser/extensions/app_shortcut_manager.cc
+++ b/chrome/browser/extensions/app_shortcut_manager.cc
@@ -17,7 +17,7 @@
 #include "skia/ext/image_operations.h"
 #include "ui/base/resource/resource_bundle.h"
 
-using extensions::Extension;
+namespace extensions {
 
 namespace {
 // Allow tests to disable shortcut creation, to prevent developers' desktops
@@ -153,3 +153,5 @@ void AppShortcutManager::DeleteApplicationShortcuts(
       ShortcutInfoForExtensionAndProfile(extension, profile_);
   web_app::DeleteAllShortcuts(delete_info);
 }
+
+}  // namespace extensions