Skip the SAML confirm password screen when a single password is scraped

chrome/browser/resources/gaia_auth_host/authenticator.js

 // Copyright 2014 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.
 
 <include src="saml_handler.js">
 
 /**
  * @fileoverview An UI component to authenciate to Chrome. The component hosts
  * IdP web pages in a webview. A client who is interested in monitoring
  * authentication events should pass a listener object of type
@@ skipping 632 matching lines @@
       if (this.noPasswordCallback) {
         this.noPasswordCallback(this.email_);
         return;
       }
 
       // Fall through to finish the auth flow even if this.needPassword
       // is true. This is because the flag is used as an intention to get
       // password when it is available but not a mandatory requirement.
       console.warn('Authenticator: No password scraped for SAML.');
     } else if (this.needPassword) {
+      if (this.samlHandler_.scrapedPasswordCount == 1) {
+        // If we scraped exactly one password, we verify that it and complete
+        // the authentication right away.
+        var passwords = this.samlHandler_.getConsolidatedScrapedPasswords_();
+        this.verifyConfirmedPassword(passwords[0]);

[xiyuan, 2016/05/04 19:35:04]

getConsolidatedScrapedPasswords_ is private and we should not call it. And
calling verifyConfirmedPassword is unnecessary. Let's just get the password and
finish the flow here.

Add a getter to saml handler, e.g.
  get firstScrapedPassword() {
    var scraped = this.getConsolidatedScrapedPasswords_();
    return scraped.length ? scraped[0] : '';
  }

then we just get that and finish the flow here:
  this.password_ = this.samlHandler_.firstScrapedPassword();
  this.onAuthCompleted_();

[afakhry, 2016/05/04 20:16:15]

Done.

+        return;
+      }
+
       if (this.confirmPasswordCallback) {
         // Confirm scraped password. The flow follows in
         // verifyConfirmedPassword.
         this.confirmPasswordCallback(this.email_,
                                      this.samlHandler_.scrapedPasswordCount);
         return;
       }
     }
 
     this.onAuthCompleted_();
@@ skipping 164 matching lines @@
   Authenticator.AuthMode = AuthMode;
   Authenticator.SUPPORTED_PARAMS = SUPPORTED_PARAMS;
 
   return {
     // TODO(guohui, xiyuan): Rename GaiaAuthHost to Authenticator once the old
     // iframe-based flow is deprecated.
     GaiaAuthHost: Authenticator,
     Authenticator: Authenticator
   };
 });