Fixing an issue with leaking starting windows. (Bug 17657878)

In some cases, when starting an animation while another starting window is visible,
the starting window is never scheduled to be removed.  In that case, we try and
schedule the closing app starting window to be removed when we are starting the
transition to a new activity.  This also partially addresses issues related to
leaking windows in b/17381033.

Change-Id: Id26525cd71380852f109ec2f55a4a60db5086ded

Author: Winson Chung

services/core/java/com/android/server/wm/WindowManagerService.java

@@ -9093,6 +9093,11 @@ public int handleAppTransitionReadyLocked(WindowList windows) {
                 // gotten drawn.
                 wtoken.allDrawn = true;
                 wtoken.deferClearAllDrawn = false;
+                // Ensure that apps that are mid-starting are also scheduled to have their
+                // starting windows removed after the animation is complete
+                if (wtoken.startingWindow != null && !wtoken.startingWindow.mExiting) {
+                    scheduleRemoveStartingWindow(wtoken);
+                }
 
                 if (animLp != null) {
                     int layer = -1;