Prevent the thread unsafe operation during the user switching

- Prevent accessing a variable that controls brightness
  at the same time through different threads.

Bug: 267255661
Bug: 262663423
Test: Manual
Change-Id: I7ffeb83e664e058a9b3e9f4f8a59d65936c43a6b
(cherry picked from commit 9e345b6844)

services/core/java/com/android/server/display/DisplayPowerController.java

@@ -132,6 +132,7 @@ final class DisplayPowerController implements AutomaticBrightnessController.Call
     private static final int MSG_UPDATE_RBC = 11;
     private static final int MSG_BRIGHTNESS_RAMP_DONE = 12;
     private static final int MSG_STATSD_HBM_BRIGHTNESS = 13;
+    private static final int MSG_SWITCH_USER = 14;
 
     private static final int PROXIMITY_UNKNOWN = -1;
     private static final int PROXIMITY_NEGATIVE = 0;
@@ -703,6 +704,11 @@ final class DisplayPowerController implements AutomaticBrightnessController.Call
     }
 
     public void onSwitchUser(@UserIdInt int newUserId) {
+        Message msg = mHandler.obtainMessage(MSG_SWITCH_USER, newUserId);
+        mHandler.sendMessage(msg);
+    }
+
+    private void handleOnSwitchUser(@UserIdInt int newUserId) {
         handleSettingsChange(true /* userSwitch */);
         handleBrightnessModeChange();
         if (mBrightnessTracker != null) {
@@ -3167,6 +3173,10 @@ final class DisplayPowerController implements AutomaticBrightnessController.Call
                 case MSG_STATSD_HBM_BRIGHTNESS:
                     logHbmBrightnessStats(Float.intBitsToFloat(msg.arg1), msg.arg2);
                     break;
+
+                case MSG_SWITCH_USER:
+                    handleOnSwitchUser(msg.arg1);
+                    break;
             }
         }
     }