[Assistant opt-in] Fix DCHECK error

Check the enrollment status before calling stop enrollment call.

Also restore a JS method that was removed accidentally recently.

Bug: 1084388, b/157268233
Test: Manual Test
Change-Id: I86826951ee2185ca0b1635278ef5b2a84358ac35
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2213241Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Yue Li <updowndota@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772044}

chrome/browser/resources/chromeos/assistant_optin/assistant_optin.js

@@ -56,6 +56,13 @@ cr.define('login.AssistantOptInFlowScreen', function() {
     onVoiceMatchUpdate(state) {
       $('assistant-optin-flow-card').onVoiceMatchUpdate(state);
     },
+
+    /**
+     * Called when the flow finished and close the dialog.
+     */
+    closeDialog() {
+      assistant.BrowserProxyImpl.getInstance().dialogClose();
+    },
   };
 });
 

chrome/browser/resources/chromeos/assistant_optin/assistant_optin_flow.js

@@ -138,7 +138,6 @@ Polymer({
       case this.$['voice-match']:
         if (this.flowType == this.FlowType.SPEAKER_ID_ENROLLMENT ||
             this.flowType == this.FlowType.SPEAKER_ID_RETRAIN) {
-          chrome.send('login.AssistantOptInFlowScreen.flowFinished');
           this.browserProxy_.flowFinished();
         } else {
           this.showScreen(this.$['get-more']);

chrome/browser/ui/webui/chromeos/login/assistant_optin_flow_screen_handler.cc

@@ -517,7 +517,8 @@ void AssistantOptInFlowScreenHandler::HandleVoiceMatchScreenUserAction(
       // No need to disable hotword for retrain flow since user has a model.
       prefs->SetBoolean(assistant::prefs::kAssistantHotwordEnabled, false);
     }
-    StopSpeakerIdEnrollment();
+    if (voice_match_enrollment_started_)
+      StopSpeakerIdEnrollment();
     ShowNextScreen();
   } else if (action == kRecordPressed) {
     if (!prefs->GetBoolean(assistant::prefs::kAssistantHotwordEnabled)) {