chromeos: set kEmbedType property for DetachedTitleAreaRendererForClient

All other code paths properly set it. Without this we hit DCHECKs as
the type isn't set.

BUG=786544
TEST=covered by tests

Change-Id: Ia3837afa9641c6fef83ed4441dbcb5ab1d5d9cd4
Reviewed-on: https://chromium-review.googlesource.com/794520Reviewed-by: Elliot Glaysher <erg@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519842}

ash/frame/detached_title_area_renderer.cc

@@ -99,6 +99,8 @@ DetachedTitleAreaRendererForClient::DetachedTitleAreaRendererForClient(
       CreateInitParams("DetachedTitleAreaRendererForClient");
   views::NativeWidgetAura* native_widget =
       new views::NativeWidgetAura(widget_, true);
+  native_widget->GetNativeView()->SetProperty(
+      aura::client::kEmbedType, aura::client::WindowEmbedType::TOP_LEVEL_IN_WM);
   aura::SetWindowType(native_widget->GetNativeWindow(),
                       ui::mojom::WindowType::POPUP);
   ApplyProperties(native_widget->GetNativeWindow(),