Pass correct task to window manager

The target task when starting is not always the top task. If it's not
the window manager gets into a bad state.

Fixes bug 14684143.

Change-Id: I90145ae43bdc5d980dc25ac19e12aa84debfed71

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

@@ -1818,7 +1818,7 @@ public final class ActivityStackSupervisor implements DisplayListener {
             }
             targetStack = sourceTask.stack;
             targetStack.moveToFront();
-            mWindowManager.moveTaskToTop(sourceTask.taskId);
+            mWindowManager.moveTaskToTop(targetStack.topTask().taskId);
             if (!addingToTask &&
                     (launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0) {
                 // In this case, we are adding the activity to an existing