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

chrome/browser/extensions/convert_web_app.h

Index: chrome/browser/extensions/convert_web_app.h
diff --git a/chrome/browser/extensions/convert_web_app.h b/chrome/browser/extensions/convert_web_app.h
index b792c5c34e4a93660d9e4f90cf20867b0203269b..0bff0e51c727c95dda6e61dcce507e46a4a5ab20 100644
--- a/chrome/browser/extensions/convert_web_app.h
+++ b/chrome/browser/extensions/convert_web_app.h
@@ -14,11 +14,10 @@ namespace base {
 class Time;
 }
 
+struct WebApplicationInfo;
+
 namespace extensions {
 class Extension;
-}
-
-struct WebApplicationInfo;
 
 // Generates a version number for an extension from a time. The goal is to make
 // use of the version number to communicate the date in a human readable form,
@@ -38,8 +37,10 @@ std::string ConvertTimeToExtensionVersion(const base::Time& time);
 // NOTE: This function does file IO and should not be called on the UI thread.
 // NOTE: The caller takes ownership of the directory at extension->path() on the
 // returned object.
-scoped_refptr<extensions::Extension> ConvertWebAppToExtension(
+scoped_refptr<Extension> ConvertWebAppToExtension(
     const WebApplicationInfo& web_app_info,
     const base::Time& create_time);
 
+}  // namespace extensions
+
 #endif  // CHROME_BROWSER_EXTENSIONS_CONVERT_WEB_APP_H_