Added multi-login support to one-click signin.

chrome/browser/signin/signin_manager.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // The signin manager encapsulates some functionality tracking
 // which user is signed in. When a user is signed in, a ClientLogin
 // request is run on their behalf. Auth tokens are fetched from Google
 // and the results are stored in the TokenService.
 //
 // **NOTE** on semantics of SigninManager:
@@ skipping 65 matching lines @@
   virtual void StartSignIn(const std::string& username,
                            const std::string& password,
                            const std::string& login_token,
                            const std::string& login_captcha);
 
   // Used when a second factor access code was required to complete a signin
   // attempt.
   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
   // associated with the user, and canceling all auth in progress.
   virtual void SignOut();
 
   // Returns true if there's a signin in progress.
   bool AuthInProgress() const;
 
   // Handles errors if a required user info key is not returned from the
@@ skipping 59 matching lines @@
 
   // Register for notifications from the TokenService.
   content::NotificationRegistrar registrar_;
 
   std::string authenticated_username_;
 
   DISALLOW_COPY_AND_ASSIGN(SigninManager);
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_SIGNIN_MANAGER_H_