Enable WidgetTestInteractive.DesktopNativeWidgetWithModalTransientChild on OS_WIN

ui/views/widget/widget_interactive_uitest.cc

Index: ui/views/widget/widget_interactive_uitest.cc
diff --git a/ui/views/widget/widget_interactive_uitest.cc b/ui/views/widget/widget_interactive_uitest.cc
index cd58ae0ec9c4f1f1bbdecf18b4cc97a2a7ea082d..8de867cf8a84d84f4c0cd03bc6c3dbc78049e088 100644
--- a/ui/views/widget/widget_interactive_uitest.cc
+++ b/ui/views/widget/widget_interactive_uitest.cc
@@ -1271,12 +1271,18 @@ TEST_F(WidgetTestInteractive, RestoreAfterMinimize) {
   widget->CloseNow();
 }
 
-#if defined(OS_LINUX) && !defined(OS_CHROMEOS) && !defined(OS_WIN)
-// TODO(warx): Investigate the flakiness on OS_WIN (crbug.com/729331).
+#if defined(OS_LINUX) && !defined(OS_CHROMEOS)
 // Tests that when a desktop native widget has modal transient child, it should
 // avoid restore focused view itself as the modal transient child window will do
 // that, thus avoids having multiple focused view visually (crbug.com/727641).
 TEST_F(WidgetTestInteractive, DesktopNativeWidgetWithModalTransientChild) {
+#if defined(OS_WIN)

[sky, 2017/06/07 16:09:34]

I get that you really only need this for windows, but will it matter on other
platforms? Can you always do it?

[Qiang(Joe) Xu, 2017/06/07 17:28:17]

yes, we can always do it. Done.

+  // On Windows, Widget::Deactivate() works by activating the next topmost
+  // window on the z-order stack. This only works if there is at least one other
+  // window, so make sure that is the case.
+  Widget* deactivate_widget = CreateWidget();
+  deactivate_widget->Show();
+#endif
   // Create a top level desktop native widget.
   Widget* top_level = CreateWidget();
 
@@ -1315,8 +1321,12 @@ TEST_F(WidgetTestInteractive, DesktopNativeWidgetWithModalTransientChild) {
   EXPECT_FALSE(textfield->HasFocus());
 
   top_level->CloseNow();
+
+#if defined(OS_WIN)
+  deactivate_widget->CloseNow();
+#endif
 }
-#endif  // defined(USE_AURA) && !defined(OS_CHROMEOS) && !defined(OS_WIN)
+#endif  // defined(USE_AURA) && !defined(OS_CHROMEOS)
 
 namespace {