cros: Add back button for the SAML interstitial

Fixed: 1051867
Change-Id: Idae22190f05a870645aa55f62d0c77dc9f366595
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2073719
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Reviewed-by: Denis Kuznetsov [CET] <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744713}

chrome/browser/chromeos/login/saml/saml_browsertest.cc

@@ -1274,6 +1274,7 @@ class SAMLPolicyTest : public SamlTest {
 
   void ShowGAIALoginForm();
   void ShowSAMLInterstitial();
+  void ClickBackOnSAMLInterstitialPage();
   void ClickNextOnSAMLInterstitialPage();
   void LogInWithSAML(const std::string& user_id,
                      const std::string& auth_sid_cookie,
@@ -1470,6 +1471,10 @@ void SAMLPolicyTest::ShowSAMLInterstitial() {
       ->Wait();
 }
 
+void SAMLPolicyTest::ClickBackOnSAMLInterstitialPage() {
+  test::OobeJS().TapOnPath({"gaia-signin", "interstitial-back"});
+}
+
 void SAMLPolicyTest::ClickNextOnSAMLInterstitialPage() {
   content::DOMMessageQueue message_queue;
   SetupAuthFlowChangeListener();
@@ -1707,6 +1712,12 @@ IN_PROC_BROWSER_TEST_F(SAMLPolicyTest, SAMLInterstitialNext) {
   SetLoginBehaviorPolicyToSAMLInterstitial();
   WaitForSigninScreen();
 
+  ShowSAMLInterstitial();
+  ClickBackOnSAMLInterstitialPage();
+  // Back button should hide OOBE dialog.
+  EXPECT_FALSE(ash::LoginScreenTestApi::IsOobeDialogVisible());
+  EXPECT_TRUE(ash::LoginScreenTestApi::IsAddUserButtonShown());
+
   ShowSAMLInterstitial();
   ClickNextOnSAMLInterstitialPage();
 

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

@@ -39,7 +39,9 @@
           slot="bottom-buttons" class="relative flex layout horizontal">
         <div id="buttons-container" class="flex layout horizontal center">
           <oobe-back-button id="signin-back-button"
-              disabled="[[!navigationEnabled_]]"></oobe-back-button>
+              disabled="[[!navigationEnabled_]]"
+              on-click="onBackButtonClicked_">
+          </oobe-back-button>
           <div class="flex">
           </div>
           <oobe-text-button id="secondary-action-button"
@@ -91,7 +93,11 @@
           </a>
         </p>
       </div>
-      <div slot="bottom-buttons" class="flex layout horizontal end-justified">
+      <div slot="bottom-buttons" class="flex layout horizontal">
+        <oobe-back-button id="interstitial-back" on-tap="onBackButtonClicked_">
+        </oobe-back-button>
+        <div class="flex">
+        </div>
         <oobe-next-button on-tap="onSamlInterstitialNext_"
             id="interstitial-next" class="focus-on-show"></oobe-next-button>
       </div>

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

@@ -415,8 +415,6 @@ Polymer({
           eventName, authenticatorEventListeners[eventName].bind(this));
     }
 
-    this.$['signin-back-button'].addEventListener(
-        'click', this.onBackButtonClicked_.bind(this));
     this.$['offline-gaia'].addEventListener(
         'offline-gaia-cancel', this.cancel.bind(this));
 
@@ -1327,8 +1325,7 @@ Polymer({
 
     // TODO(crbug.com/470893): Figure out whether/which of these exit conditions
     // are useful.
-    if (this.screenMode_ == AuthMode.SAML_INTERSTITIAL ||
-        this.isWhitelistErrorShown_ || this.authCompleted_) {
+    if (this.isWhitelistErrorShown_ || this.authCompleted_) {
       return;
     }