Update getUserSwitchability() to handle different user ids and Auto

User switcher is in SystemUI which runs in User 0.
UserManager.getUserSwitchability() currently checks for the
DISALLOW_USER_SWITCH only on the process's user id rather than the
foreground user's id. This is causing a bug where we're using the wrong
user to check for user restrictions.

This CL updates getUserSwitchability to handle different user ids and
updates UserSwitcherController to use the new API.

This also introduces Headless System User support which only runs a
subset of the logic.

Fixes: 143298605
Test: [1] Enable multi-user
[2] Create a new secondary user
[3] Switch to new secondary user (assume to be user 10)
[4] adb root && adb shell pm set-user-restriction --user 10 no_user_switch 1
[5] Can't user switch
[6] adb root && adb shell pm set-user-restriction --user 10 no_user_switch 0
[7] Can user switch

Change-Id: Id039e2afd01a53116700c08177eb4e599a871946
diff --git a/core/java/android/os/UserManager.java b/core/java/android/os/UserManager.java
index 71b94ed..b7a3c8f 100644
--- a/core/java/android/os/UserManager.java
+++ b/core/java/android/os/UserManager.java
@@ -1314,7 +1314,8 @@
     }
 
     /**
-     * Returns whether switching users is currently allowed.
+     * Returns whether switching users is currently allowed for the user this process is running
+     * under.
      * <p>
      * Switching users is not allowed in the following cases:
      * <li>the user is in a phone call</li>
@@ -1329,10 +1330,24 @@
             android.Manifest.permission.MANAGE_USERS,
             android.Manifest.permission.INTERACT_ACROSS_USERS}, conditional = true)
     public @UserSwitchabilityResult int getUserSwitchability() {
-        final boolean allowUserSwitchingWhenSystemUserLocked = Settings.Global.getInt(
-                mContext.getContentResolver(),
-                Settings.Global.ALLOW_USER_SWITCHING_WHEN_SYSTEM_USER_LOCKED, 0) != 0;
-        final boolean systemUserUnlocked = isUserUnlocked(UserHandle.SYSTEM);
+        return getUserSwitchability(Process.myUserHandle());
+    }
+
+    /**
+     * Returns whether switching users is currently allowed for the provided user.
+     * <p>
+     * Switching users is not allowed in the following cases:
+     * <li>the user is in a phone call</li>
+     * <li>{@link #DISALLOW_USER_SWITCH} is set</li>
+     * <li>system user hasn't been unlocked yet</li>
+     *
+     * @return A {@link UserSwitchabilityResult} flag indicating if the user is switchable.
+     * @hide
+     */
+    @RequiresPermission(allOf = {Manifest.permission.READ_PHONE_STATE,
+            android.Manifest.permission.MANAGE_USERS,
+            android.Manifest.permission.INTERACT_ACROSS_USERS}, conditional = true)
+    public @UserSwitchabilityResult int getUserSwitchability(UserHandle userHandle) {
         final TelephonyManager tm =
                 (TelephonyManager) mContext.getSystemService(Context.TELEPHONY_SERVICE);
 
@@ -1340,12 +1355,22 @@
         if (tm.getCallState() != TelephonyManager.CALL_STATE_IDLE) {
             flags |= SWITCHABILITY_STATUS_USER_IN_CALL;
         }
-        if (hasUserRestriction(DISALLOW_USER_SWITCH)) {
+        if (hasUserRestriction(DISALLOW_USER_SWITCH, userHandle)) {
             flags |= SWITCHABILITY_STATUS_USER_SWITCH_DISALLOWED;
         }
-        if (!allowUserSwitchingWhenSystemUserLocked && !systemUserUnlocked) {
-            flags |= SWITCHABILITY_STATUS_SYSTEM_USER_LOCKED;
+
+        // System User is always unlocked in Headless System User Mode, so ignore this flag
+        if (!isHeadlessSystemUserMode()) {
+            final boolean allowUserSwitchingWhenSystemUserLocked = Settings.Global.getInt(
+                    mContext.getContentResolver(),
+                    Settings.Global.ALLOW_USER_SWITCHING_WHEN_SYSTEM_USER_LOCKED, 0) != 0;
+            final boolean systemUserUnlocked = isUserUnlocked(UserHandle.SYSTEM);
+
+            if (!allowUserSwitchingWhenSystemUserLocked && !systemUserUnlocked) {
+                flags |= SWITCHABILITY_STATUS_SYSTEM_USER_LOCKED;
+            }
         }
+
         return flags;
     }
 
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/policy/UserSwitcherController.java b/packages/SystemUI/src/com/android/systemui/statusbar/policy/UserSwitcherController.java
index f2d2fae..2c99668 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/policy/UserSwitcherController.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/policy/UserSwitcherController.java
@@ -16,6 +16,8 @@
 
 package com.android.systemui.statusbar.policy;
 
+import static android.os.UserManager.SWITCHABILITY_STATUS_OK;
+
 import static com.android.settingslib.RestrictedLockUtils.EnforcedAdmin;
 import static com.android.systemui.DejankUtils.whitelistIpcs;
 
@@ -196,7 +198,10 @@
                 }
                 ArrayList<UserRecord> records = new ArrayList<>(infos.size());
                 int currentId = ActivityManager.getCurrentUser();
-                boolean canSwitchUsers = mUserManager.canSwitchUsers();
+                // Check user switchability of the foreground user since SystemUI is running in
+                // User 0
+                boolean canSwitchUsers = mUserManager.getUserSwitchability(
+                        UserHandle.of(ActivityManager.getCurrentUser())) == SWITCHABILITY_STATUS_OK;
                 UserInfo currentUserInfo = null;
                 UserRecord guestRecord = null;