Check session state when showing Assistant opt-in dialog

In order to prevent corner cases/timing issue related to session state
change, adding a check when showing the opt-in dialog.

Bug: 978267
Test: Run existing tests
Change-Id: I9f84e5fc90ba8d50407fa44a29749406ae1b2db0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1717464Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Yue Li <updowndota@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681062}

chrome/browser/ui/webui/chromeos/assistant_optin/assistant_optin_ui.cc

@@ -22,6 +22,7 @@
 #include "chromeos/services/assistant/public/cpp/assistant_prefs.h"
 #include "components/arc/arc_prefs.h"
 #include "components/prefs/pref_service.h"
+#include "components/session_manager/core/session_manager.h"
 #include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/url_data_source.h"
 #include "content/public/browser/web_ui.h"
@@ -118,6 +119,12 @@ void AssistantOptInUI::Initialize() {
 void AssistantOptInDialog::Show(
     ash::FlowType type,
     ash::AssistantSetup::StartAssistantOptInFlowCallback callback) {
+  // Check session state here to prevent timing issue -- session state might
+  // have changed during the mojom calls to launch the opt-in dalog.
+  if (session_manager::SessionManager::Get()->session_state() !=
+      session_manager::SessionState::ACTIVE) {
+    return;
+  }
   if (g_dialog) {
     g_dialog->Focus();
     std::move(callback).Run(false);