Reland of Clear the login webview when SAML flow is canceled

chrome/browser/resources/chromeos/login/screen_gaia_signin.js

Index: chrome/browser/resources/chromeos/login/screen_gaia_signin.js
diff --git a/chrome/browser/resources/chromeos/login/screen_gaia_signin.js b/chrome/browser/resources/chromeos/login/screen_gaia_signin.js
index 112edf5bccbc728f0f1ef879829562146c7932fe..e61d4f43d3d7c2bc4af7c8e80b35002feba3a63c 100644
--- a/chrome/browser/resources/chromeos/login/screen_gaia_signin.js
+++ b/chrome/browser/resources/chromeos/login/screen_gaia_signin.js
@@ -557,6 +557,13 @@ login.createScreen('GaiaSigninScreen', 'gaia-signin', function() {
      * @private
      */
     loadAuthExtension: function(data) {
+      // Redirect the webview to the blank page in order to stop the SAML IdP
+      // page from working in a background (see crbug.com/613245).
+      if (this.screenMode_ == ScreenMode.DEFAULT &&
+          data.screenMode != ScreenMode.DEFAULT) {
+        this.gaiaAuthHost_.resetWebview();
+      }
+
       this.screenMode = data.screenMode;
       this.email = '';
       this.authCompleted_ = false;
@@ -923,7 +930,7 @@ login.createScreen('GaiaSigninScreen', 'gaia-signin', function() {
      */
     reset: function(takeFocus, forceOnline) {
       // Reload and show the sign-in UI if needed.
-      this.gaiaAuthHost_.resetStates_();
+      this.gaiaAuthHost_.resetStates();
       if (takeFocus) {
         if (!forceOnline && this.isOffline()) {
           // Show 'Cancel' button to allow user to return to the main screen