Chromad: Add authentication flow

chrome/browser/chromeos/login/helper.h

Index: chrome/browser/chromeos/login/helper.h
diff --git a/chrome/browser/chromeos/login/helper.h b/chrome/browser/chromeos/login/helper.h
index c2d0d7f5b46ab69cd99b1fd4087d2c2062fc826f..ff139ca888a8bc10caca6c85fa9f244505bf56b6 100644
--- a/chrome/browser/chromeos/login/helper.h
+++ b/chrome/browser/chromeos/login/helper.h
@@ -110,6 +110,10 @@ content::StoragePartition* GetSigninPartition();
 // flow, the context of the sign-in webview storage partition is returned.
 net::URLRequestContextGetter* GetSigninContext();
 
+using OnPipeReadyCallback = base::Callback<void(base::ScopedFD fd)>;
+void GetPipeReadEnd(const std::string& data,
+                    const OnPipeReadyCallback& callback);
+
 }  // namespace login
 
 }  // namespace chromeos