More eagerly collect isSimpleUserSwitcher.

This is a blind attempt to fix the attached bug. The hypothesis is that
there's a race condition between when this is queried by the large
screen bouncer user switching drop-down and the coroutine job that
hydrates this flow with values.

The approach in this CL is to sacrifice some startup performance to make
the value available as early as possible as to avoid the race condition.

Bug: 256698234
Test: all existing user-related unit and integration tests pass locally
Test: manually verified on both small and large screen devices that the
popup and full-screen user switcher, respectively, show up
Test: manually verified, on large screen, that the bouncer
user-switching drop-down shows up and works

Change-Id: I431dbace23f8472a296b374739729a9867efe8ea

packages/SystemUI/src/com/android/systemui/user/data/repository/UserRepository.kt

@@ -47,12 +47,14 @@ import kotlinx.coroutines.asExecutor
 import kotlinx.coroutines.channels.awaitClose
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.flow.onStart
+import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.withContext
@@ -120,9 +122,25 @@ constructor(
     featureFlags: FeatureFlags,
 ) : UserRepository {
 
-    private val _userSwitcherSettings = MutableStateFlow(runBlocking { getSettings() })
-    override val userSwitcherSettings: Flow<UserSwitcherSettingsModel> =
-        _userSwitcherSettings.asStateFlow().filterNotNull()
+    private val _userSwitcherSettings: StateFlow<UserSwitcherSettingsModel> =
+        globalSettings
+            .observerFlow(
+                names =
+                    arrayOf(
+                        SETTING_SIMPLE_USER_SWITCHER,
+                        Settings.Global.ADD_USERS_WHEN_LOCKED,
+                        Settings.Global.USER_SWITCHER_ENABLED,
+                    ),
+                userId = UserHandle.USER_SYSTEM,
+            )
+            .onStart { emit(Unit) } // Forces an initial update.
+            .map { getSettings() }
+            .stateIn(
+                scope = applicationScope,
+                started = SharingStarted.Eagerly,
+                initialValue = runBlocking { getSettings() },
+            )
+    override val userSwitcherSettings: Flow<UserSwitcherSettingsModel> = _userSwitcherSettings
 
     private val _userInfos = MutableStateFlow<List<UserInfo>?>(null)
     override val userInfos: Flow<List<UserInfo>> = _userInfos.filterNotNull()
@@ -154,7 +172,6 @@ constructor(
 
     init {
         observeSelectedUser()
-        observeUserSettings()
         if (featureFlags.isEnabled(FACE_AUTH_REFACTOR)) {
             observeUserSwitching()
         }
@@ -237,23 +254,6 @@ constructor(
             .launchIn(applicationScope)
     }
 
-    private fun observeUserSettings() {
-        globalSettings
-            .observerFlow(
-                names =
-                    arrayOf(
-                        SETTING_SIMPLE_USER_SWITCHER,
-                        Settings.Global.ADD_USERS_WHEN_LOCKED,
-                        Settings.Global.USER_SWITCHER_ENABLED,
-                    ),
-                userId = UserHandle.USER_SYSTEM,
-            )
-            .onStart { emit(Unit) } // Forces an initial update.
-            .map { getSettings() }
-            .onEach { _userSwitcherSettings.value = it }
-            .launchIn(applicationScope)
-    }
-
     private suspend fun getSettings(): UserSwitcherSettingsModel {
         return withContext(backgroundDispatcher) {
             val isSimpleUserSwitcher =