Issue a warning when the user switching dialog times out.

Example:

11-22 06:44:38.846  2825  2842 W ActivityManagerUserSwitchingDialog: user switch window not shown in 3000 ms

Bug: 145001354
Test: manual verification

Change-Id: I2dc748ea43df227d9f07e6743e39ae25a096352a
(cherry picked from commit 72a052308f67b72c8abba231568f8c93e7e6ec07)

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

@@ -24,6 +24,7 @@ import android.os.Handler;
 import android.os.Message;
 import android.os.UserHandle;
 import android.os.UserManager;
+import android.util.Slog;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewTreeObserver;
@@ -46,6 +47,8 @@ class UserSwitchingDialog extends AlertDialog
     // Time to wait for the onWindowShown() callback before continuing the user switch
     private static final int WINDOW_SHOWN_TIMEOUT_MS = 3000;
 
+    private static final boolean DEBUG = false;
+
     private final ActivityManagerService mService;
     private final int mUserId;
     private static final int MSG_START_USER = 1;
@@ -118,7 +121,7 @@ class UserSwitchingDialog extends AlertDialog
 
     @Override
     public void show() {
-        // Slog.v(TAG, "show called");
+        if (DEBUG) Slog.d(TAG, "show called");
         super.show();
         final View decorView = getWindow().getDecorView();
         if (decorView != null) {
@@ -132,13 +135,14 @@ class UserSwitchingDialog extends AlertDialog
 
     @Override
     public void onWindowShown() {
-        // Slog.v(TAG, "onWindowShown called");
+        if (DEBUG) Slog.d(TAG, "onWindowShown called");
         startUser();
     }
 
     void startUser() {
         synchronized (this) {
             if (!mStartedUser) {
+                Slog.i(TAG, "starting user " + mUserId);
                 mService.mUserController.startUserInForeground(mUserId);
                 dismiss();
                 mStartedUser = true;
@@ -147,6 +151,8 @@ class UserSwitchingDialog extends AlertDialog
                     decorView.getViewTreeObserver().removeOnWindowShownListener(this);
                 }
                 mHandler.removeMessages(MSG_START_USER);
+            } else {
+                Slog.i(TAG, "user " + mUserId + " already started");
             }
         }
     }
@@ -156,6 +162,8 @@ class UserSwitchingDialog extends AlertDialog
         public void handleMessage(Message msg) {
             switch (msg.what) {
                 case MSG_START_USER:
+                    Slog.w(TAG, "user switch window not shown in "
+                            + WINDOW_SHOWN_TIMEOUT_MS + " ms");
                     startUser();
                     break;
             }