Remove redundant call to window manager addTask()

If there are activities in persisted tasks then calling addAppToken()
will automatically call addTask(). If there are no activities then
calling addTask() is a nop. In either case the call to addTask() is
unnecessary. It was actually worse than unnecessary because in the
former case we ended up with two identical tasks in the Window
Manager.

Fixes bug 16958544.

Change-Id: I2dc4b50aa94668873c1a783c47e0c696d62616f0

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

@@ -2430,7 +2430,6 @@ public final class ActivityStackSupervisor implements DisplayListener {
                         r.userId, r.info.configChanges, task.voiceSession != null,
                         r.mLaunchTaskBehind);
             }
-            mWindowManager.addTask(taskId, stackId, false);
         }
         resumeHomeStackTask(HOME_ACTIVITY_TYPE, null);
     }