Clear AssistantState reference if it is freed.

AssistantState might be freed when QuickAnswersClient destructor is
called (for example, in unit tests).

Bug: b/144314551
Test: Unit tests
Change-Id: Ib088e3eb2f1e1d3797a698bd10bbef16b1f3bd13
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2012910Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Tao Wu <wutao@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: Li Lin <llin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733794}

ash/public/cpp/assistant/assistant_state_base.cc

@@ -30,7 +30,10 @@ void PrintValue(std::stringstream* result,
 
 AssistantStateBase::AssistantStateBase() = default;
 
-AssistantStateBase::~AssistantStateBase() = default;
+AssistantStateBase::~AssistantStateBase() {
+  for (auto& observer : observers_)
+    observer.OnAssistantStateDestroyed();
+}
 
 std::string AssistantStateBase::ToString() const {
   std::stringstream result;

ash/public/cpp/assistant/assistant_state_base.h

@@ -35,6 +35,7 @@ class ASH_PUBLIC_EXPORT AssistantStateObserver
   virtual void OnAssistantHotwordEnabled(bool enabled) {}
   virtual void OnAssistantLaunchWithMicOpen(bool launch_with_mic_open) {}
   virtual void OnAssistantNotificationEnabled(bool notification_enabled) {}
+  virtual void OnAssistantStateDestroyed() {}
 
   // mojom::AssistantStateObserver:
   void OnAssistantStatusChanged(mojom::AssistantState state) override {}

chromeos/components/quick_answers/quick_answers_client.cc

@@ -46,13 +46,16 @@ QuickAnswersClient::QuickAnswersClient(URLLoaderFactory* url_loader_factory,
     : url_loader_factory_(url_loader_factory),
       assistant_state_(assistant_state),
       delegate_(delegate) {
-  // We observe Assistant state to detect enabling/disabling of Assistant in
-  // settings as well as enabling/disabling of screen context.
-  assistant_state_->AddObserver(this);
+  if (assistant_state_) {
+    // We observe Assistant state to detect enabling/disabling of Assistant in
+    // settings as well as enabling/disabling of screen context.
+    assistant_state_->AddObserver(this);
+  }
 }
 
 QuickAnswersClient::~QuickAnswersClient() {
-  assistant_state_->RemoveObserver(this);
+  if (assistant_state_)
+    assistant_state_->RemoveObserver(this);
 }
 
 void QuickAnswersClient::OnAssistantFeatureAllowedChanged(
@@ -79,6 +82,10 @@ void QuickAnswersClient::OnLocaleChanged(const std::string& locale) {
   NotifyEligibilityChanged();
 }
 
+void QuickAnswersClient::OnAssistantStateDestroyed() {
+  assistant_state_ = nullptr;
+}
+
 void QuickAnswersClient::SendRequest(
     const QuickAnswersRequest& quick_answers_request) {
   // Preprocess the request.
@@ -96,8 +103,8 @@ void QuickAnswersClient::SendRequest(
 void QuickAnswersClient::NotifyEligibilityChanged() {
   DCHECK(delegate_);
   bool is_eligible =
-      (chromeos::features::IsQuickAnswersEnabled() && assistant_enabled_ &&
-       locale_supported_ && assistant_context_enabled_ &&
+      (chromeos::features::IsQuickAnswersEnabled() && assistant_state_ &&
+       assistant_enabled_ && locale_supported_ && assistant_context_enabled_ &&
        assistant_allowed_state_ == ash::mojom::AssistantAllowedState::ALLOWED);
 
   if (is_eligible_ != is_eligible) {

chromeos/components/quick_answers/quick_answers_client.h

@@ -64,6 +64,7 @@ class QuickAnswersClient : public ash::AssistantStateObserver {
   void OnAssistantSettingsEnabled(bool enabled) override;
   void OnAssistantContextEnabled(bool enabled) override;
   void OnLocaleChanged(const std::string& locale) override;
+  void OnAssistantStateDestroyed() override;
 
   // Send a quick answer request.
   void SendRequest(const QuickAnswersRequest& quick_answers_request);