Support creation of toplevel mus::Windows on separate displays

ash/mus/test/wm_test_base.cc

Index: ash/mus/test/wm_test_base.cc
diff --git a/ash/mus/test/wm_test_base.cc b/ash/mus/test/wm_test_base.cc
index c45eb6e73457fd27f8e573754940c7f90f90f533..71192e1ad21e206aaf9556cef68222bdef29d096 100644
--- a/ash/mus/test/wm_test_base.cc
+++ b/ash/mus/test/wm_test_base.cc
@@ -123,11 +123,16 @@ ui::Window* WmTestBase::CreateTestWindow(const gfx::Rect& bounds,
   return window;
 }
 
-ui::Window* WmTestBase::CreateFullscreenTestWindow() {
+ui::Window* WmTestBase::CreateFullscreenTestWindow(int64_t display_id = 0) {
   std::map<std::string, std::vector<uint8_t>> properties;
   properties[ui::mojom::WindowManager::kShowState_Property] =
       mojo::ConvertTo<std::vector<uint8_t>>(
           static_cast<int32_t>(ui::mojom::ShowState::FULLSCREEN));
+
+  if (display_id)

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

Need braces around multiline statement.

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

Done.

+    properties[ui::mojom::WindowManager::kInitialDisplayId_Property] =
+        mojo::ConvertTo<std::vector<uint8_t>>(display_id);

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

Is 0 display id guaranteed to be the same as having no display id? Because as is
if I call CreateFullscreenTestWindow(0), it won't set kInitialDisplayId_Property
prop.

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

Done. I change from 0 to display::Display::kInvalidDisplayID instead.

[mfomitchev, 2016/11/22 22:53:16]

Wait, this is different. Now we can't call this method w/o giving it a display
id - it won't work.

+
   ui::Window* window = test_helper_->GetRootsOrderedByDisplayId()[0]
                            ->window_manager()
                            ->NewTopLevelWindow(&properties);