Add trace logs to UserSwitchObserver callbacks.

UserSwitchObservers have a reply mechanism to know when the
observers finish doing their job on onUserSwitching event.
These callbacks were not shown on perfetto traces. Adding these
will be helpful to see when each callback is called while
investigating perfetto traces. Note that these traces won't be able
to show the duration of the work done by the observers since beginning
and end calls can be on different threads. But they will mark the
callbacks on the timetable of perfetto ui.

Bug: 256604395
Test: N/A
Change-Id: Ib1c76554caa472da99e86f6368611d0d251c25db

services/core/java/com/android/server/am/UserController.java

@@ -2075,6 +2075,8 @@ class UserController implements Handler.Callback {
     }
 
     private void timeoutUserSwitch(UserState uss, int oldUserId, int newUserId) {
+        TimingsTraceAndSlog t = new TimingsTraceAndSlog(TAG);
+        t.traceBegin("timeoutUserSwitch-" + oldUserId + "-to-" + newUserId);
         synchronized (mLock) {
             Slogf.e(TAG, "User switch timeout: from " + oldUserId + " to " + newUserId);
             mTimeoutUserSwitchCallbacks = mCurWaitingUserSwitchCallbacks;
@@ -2084,6 +2086,7 @@ class UserController implements Handler.Callback {
             mHandler.sendMessageDelayed(mHandler.obtainMessage(USER_SWITCH_CALLBACKS_TIMEOUT_MSG,
                     oldUserId, newUserId), USER_SWITCH_CALLBACKS_TIMEOUT_MS);
         }
+        t.traceEnd();
     }
 
     private void timeoutUserSwitchCallbacks(int oldUserId, int newUserId) {
@@ -2141,6 +2144,8 @@ class UserController implements Handler.Callback {
                                             + " ms after dispatchUserSwitch.");
                                 }
 
+                                TimingsTraceAndSlog t2 = new TimingsTraceAndSlog(TAG);
+                                t2.traceBegin("onUserSwitchingReply-" + name);
                                 curWaitingUserSwitchCallbacks.remove(name);
                                 // Continue switching if all callbacks have been notified and
                                 // user switching session is still valid
@@ -2149,11 +2154,15 @@ class UserController implements Handler.Callback {
                                         == mCurWaitingUserSwitchCallbacks)) {
                                     sendContinueUserSwitchLU(uss, oldUserId, newUserId);
                                 }
+                                t2.traceEnd();
                             }
                         }
                     };
+                    t.traceBegin("onUserSwitching-" + name);
                     mUserSwitchObservers.getBroadcastItem(i).onUserSwitching(newUserId, callback);
+                    t.traceEnd();
                 } catch (RemoteException e) {
+                    // Ignore
                 }
             }
         } else {
@@ -2167,10 +2176,13 @@ class UserController implements Handler.Callback {
 
     @GuardedBy("mLock")
     private void sendContinueUserSwitchLU(UserState uss, int oldUserId, int newUserId) {
+        TimingsTraceAndSlog t = new TimingsTraceAndSlog(TAG);
+        t.traceBegin("sendContinueUserSwitchLU-" + oldUserId + "-to-" + newUserId);
         mCurWaitingUserSwitchCallbacks = null;
         mHandler.removeMessages(USER_SWITCH_TIMEOUT_MSG);
         mHandler.sendMessage(mHandler.obtainMessage(CONTINUE_USER_SWITCH_MSG,
                 oldUserId, newUserId, uss));
+        t.traceEnd();
     }
 
     @VisibleForTesting