mojo filesystem: Further clean ups.

components/filesystem/file_system_app.h

Index: components/filesystem/file_system_app.h
diff --git a/components/filesystem/file_system_app.h b/components/filesystem/file_system_app.h
index ae624691e7d70c86f1de7d869fe53d4d7c95ded6..d116c0fa9d74804847439df93c84ad4eb4c47e40 100644
--- a/components/filesystem/file_system_app.h
+++ b/components/filesystem/file_system_app.h
@@ -27,6 +27,9 @@ class FileSystemApp : public mojo::ShellClient,
   ~FileSystemApp() override;
 
  private:
+  // Gets the system specific toplevel profile directory.
+  static base::FilePath GetUserDataDir();
+
   // |mojo::ShellClient| override:
   void Initialize(mojo::Shell* shell, const std::string& url,
                   uint32_t id) override;