Support creation of toplevel mus::Windows on separate displays

ash/mus/test/wm_test_base.h

Index: ash/mus/test/wm_test_base.h
diff --git a/ash/mus/test/wm_test_base.h b/ash/mus/test/wm_test_base.h
index 8c17d39f29eff12eae1f9b1ad7ff7056c9f8e89e..288581e073452beb3f873aa415a5ab15e9c1bb43 100644
--- a/ash/mus/test/wm_test_base.h
+++ b/ash/mus/test/wm_test_base.h
@@ -58,7 +58,8 @@ class WmTestBase : public testing::Test {
   ui::Window* CreateTestWindow(const gfx::Rect& bounds);
   ui::Window* CreateTestWindow(const gfx::Rect& bounds,
                                ui::wm::WindowType window_type);
-  ui::Window* CreateFullscreenTestWindow();
+
+  ui::Window* CreateFullscreenTestWindow(int64_t display_id);

[mfomitchev, 2016/11/18 21:23:40]

Please put the default value (int64_t display_id = 0) in the declaration as it
is essential. Also, please document the method, particularly how display_id is
used.

[thanhph, 2016/11/21 14:37:53]

Done.

 
   // Creates a window parented to |parent|. The returned window is visible.
   ui::Window* CreateChildTestWindow(ui::Window* parent,