Add convert_web_app.*, a utility to convert web apps declared

chrome/browser/extensions/convert_user_script.h

Index: chrome/browser/extensions/convert_user_script.h
diff --git a/chrome/browser/extensions/convert_user_script.h b/chrome/browser/extensions/convert_user_script.h
index d779de04c8eebef476fffa1812a577744ddc481b..678c6eb262742cefaba0a315a57f253c8deae77e 100644
--- a/chrome/browser/extensions/convert_user_script.h
+++ b/chrome/browser/extensions/convert_user_script.h
@@ -19,6 +19,8 @@ class GURL;
 // should take ownership on success, or NULL and |error| on failure.
 //
 // 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<Extension> ConvertUserScriptToExtension(
     const FilePath& user_script, const GURL& original_url, std::string* error);