aura: Ask the WindowDelegate before a Window is Focus()ed.

ui/aura/test/test_window_delegate.cc

Index: ui/aura/test/test_window_delegate.cc
diff --git a/ui/aura/test/test_window_delegate.cc b/ui/aura/test/test_window_delegate.cc
index 4244879a48df5d173538f49195c96a39073b06d3..4a4f778aae19114b0ecaca72fd15e7633385a28b 100644
--- a/ui/aura/test/test_window_delegate.cc
+++ b/ui/aura/test/test_window_delegate.cc
@@ -56,6 +56,10 @@ ui::TouchStatus TestWindowDelegate::OnTouchEvent(TouchEvent* event) {
   return ui::TOUCH_STATUS_UNKNOWN;
 }
 
+bool TestWindowDelegate::CanFocus() {
+  return true;
+}
+
 bool TestWindowDelegate::ShouldActivate(Event* event) {
   return true;
 }