Make ScopedWindowTargeter add itself as a WindowObserver for real

ui/aura/window_targeter_unittest.cc

Index: ui/aura/window_targeter_unittest.cc
diff --git a/ui/aura/window_targeter_unittest.cc b/ui/aura/window_targeter_unittest.cc
index f14d3379ea3d1113305578e1cd2b06330b8a96b3..86bd8d804da87ba7fddcd8fe1499db1175801425 100644
--- a/ui/aura/window_targeter_unittest.cc
+++ b/ui/aura/window_targeter_unittest.cc
@@ -118,6 +118,21 @@ TEST_F(WindowTargeterTest, ScopedWindowTargeter) {
   }
 }
 
+// Test that ScopedWindowTargeter does not crash if the window for which it
+// replaces the targeter gets destroyed before it does.
+TEST_F(WindowTargeterTest, ScopedWindowTargeterWindowDestroyed) {
+  test::TestWindowDelegate delegate;
+  scoped_ptr<Window> window(CreateNormalWindow(1, root_window(), &delegate));
+  scoped_ptr<ScopedWindowTargeter> scoped_targeter(
+      new ScopedWindowTargeter(window.get(), scoped_ptr<ui::EventTargeter>(
+          new StaticWindowTargeter(window.get()))));
+
+  window.reset();
+  scoped_targeter.reset();
+
+  // We did not crash!
+}
+
 TEST_F(WindowTargeterTest, TargetTransformedWindow) {
   root_window()->Show();