Reland "Add a new test case for |AssistantManagerServiceImpl|."

This is a reland of 64cf44e2

Original change's description:
> Add a new test case for |AssistantManagerServiceImpl|.
> 
> This CL adds a new test case to ensure we update the supported action
> list stored in |AssistantManagerServiceImpl| when ambient mode state has
> changed.
> 
> Bug: b/149237062
> Test: run the new unit test added in this change.
> 
> Change-Id: Idc3c538e023cb59e76fb6c71219e4846da6d9c30
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1969777
> Commit-Queue: Meilin Wang <meilinw@chromium.org>
> Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#740817}

Bug: b/149237062
Change-Id: I56f942df9293808a2411272022fe3cf3923096f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2053287Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: Meilin Wang <meilinw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741170}

chromeos/services/assistant/assistant_manager_service_impl.cc

@@ -314,9 +314,6 @@ void AssistantManagerServiceImpl::SetAccessToken(
 }
 
 void AssistantManagerServiceImpl::EnableAmbientMode(bool enabled) {
-  if (!assistant_manager_)
-    return;
-
   // Update |action_module_| accordingly, as some actions, e.g. open URL
   // in the browser, are not supported in ambient mode.
   action_module_->SetAmbientModeEnabled(enabled);
@@ -460,6 +457,8 @@ void AssistantManagerServiceImpl::SyncDeviceAppsStatus() {
 }
 
 void AssistantManagerServiceImpl::StartVoiceInteraction() {
+  DCHECK(assistant_manager_);
+
   platform_api_->SetMicState(true);
   assistant_manager_->StartAssistantInteraction();
 }
@@ -479,7 +478,7 @@ void AssistantManagerServiceImpl::StopActiveInteraction(
 void AssistantManagerServiceImpl::StartWarmerWelcomeInteraction(
     int num_warmer_welcome_triggered,
     bool allow_tts) {
-  DCHECK(assistant_manager_internal_ != nullptr);
+  DCHECK(assistant_manager_internal_);
 
   const std::string interaction =
       CreateWarmerWelcomeInteraction(num_warmer_welcome_triggered);

chromeos/services/assistant/assistant_manager_service_impl.h

@@ -235,6 +235,11 @@ class COMPONENT_EXPORT(ASSISTANT_SERVICE) AssistantManagerServiceImpl
   // thread is finished.
   void WaitUntilStartIsFinishedForTesting();
 
+  // Get the action module for testing.
+  action::CrosActionModule* action_module_for_testing() {
+    return action_module_.get();
+  }
+
  private:
   class AssistantMediaSessionObserver;
   void StartAssistantInternal(const base::Optional<std::string>& access_token);

chromeos/services/assistant/assistant_manager_service_impl_unittest.cc

@@ -221,6 +221,10 @@ class AssistantManagerServiceImplTest : public testing::Test {
     return delegate_->assistant_manager_internal();
   }
 
+  action::CrosActionModule* action_module() {
+    return assistant_manager_service_->action_module_for_testing();
+  }
+
   void Start() {
     assistant_manager_service()->Start("dummy-access-token",
                                        /*enable_hotword=*/false);
@@ -542,5 +546,16 @@ TEST_F(AssistantManagerServiceImplTest,
   Start();
 }
 
+TEST_F(AssistantManagerServiceImplTest,
+       ShouldUpdateActionModuleWhenAmbientModeStateChanged) {
+  EXPECT_FALSE(action_module()->IsAmbientModeEnabledForTesting());
+
+  assistant_manager_service()->EnableAmbientMode(true);
+  EXPECT_TRUE(action_module()->IsAmbientModeEnabledForTesting());
+
+  assistant_manager_service()->EnableAmbientMode(false);
+  EXPECT_FALSE(action_module()->IsAmbientModeEnabledForTesting());
+}
+
 }  // namespace assistant
 }  // namespace chromeos