Fix BackdropFrameRenderer leak

Make sure to stop the thread when the window gets detached. When dismissing
the docked/fullscreen stack with the divider, we stop the activity while
we are still in resizing mode.

Bug: 28054032
Change-Id: I2d5d0ffaa9bc47e4d5252414b9a045beaebb7a69

core/java/com/android/internal/policy/DecorView.java

@@ -1458,6 +1458,8 @@ public class DecorView extends FrameLayout implements RootViewSurfaceTaker, Wind
             st.menu.close();
         }
 
+        releaseThreadedRenderer();
+
         if (mWindowResizeCallbacksAdded) {
             getViewRootImpl().removeWindowCallbacks(this);
             mWindowResizeCallbacksAdded = false;