Added multi-login support to one-click signin.

chrome/browser/signin/signin_manager.h

Index: chrome/browser/signin/signin_manager.h
diff --git a/chrome/browser/signin/signin_manager.h b/chrome/browser/signin/signin_manager.h
index 0ca9d9c6b02cdff60697fab6325dce14f2a28c4b..f7098adac3294d023111da9f1dc9c798320a6505 100644
--- a/chrome/browser/signin/signin_manager.h
+++ b/chrome/browser/signin/signin_manager.h
@@ -83,8 +83,11 @@ class SigninManager : public GaiaAuthConsumer,
   void ProvideSecondFactorAccessCode(const std::string& access_code);
 
   // Attempt to sign in this user with existing credentials from the cookie jar.
-  // Otherwise the result is the same as StartSignIn().
-  virtual void StartSignInWithCredentials(const std::string& username,
+  // |session_index| indicates which user account to use if the cookie jar
+  // contains a multi-login session. Otherwise the end result of this call is
+  // the same as StartSignIn().
+  virtual void StartSignInWithCredentials(const std::string& session_index,
+                                          const std::string& username,
                                           const std::string& password);
 
   // Sign a user out, removing the preference, erasing all keys