Converts most of WorkspaceLayoutManager tests to use common code

ash/mus/test/ash_test_impl_mus.cc

Index: ash/mus/test/ash_test_impl_mus.cc
diff --git a/ash/mus/test/ash_test_impl_mus.cc b/ash/mus/test/ash_test_impl_mus.cc
index e530ebe245a1a932ea53ca172b7f4422e86b6a3b..6736ab3fa7059a2dfa4d97a30cb5951b3acaf2fc 100644
--- a/ash/mus/test/ash_test_impl_mus.cc
+++ b/ash/mus/test/ash_test_impl_mus.cc
@@ -65,6 +65,15 @@ std::unique_ptr<WindowOwner> AshTestImplMus::CreateTestWindow(
   return base::MakeUnique<WindowOwner>(window);
 }
 
+std::unique_ptr<WindowOwner> AshTestImplMus::CreateToplevelTestWindow(
+    const gfx::Rect& bounds_in_screen,
+    int shell_window_id) {
+  // For mus CreateTestWindow() creates top level windows (assuming
+  // WINDOW_TYPE_NORMAL).
+  return CreateTestWindow(bounds_in_screen, ui::wm::WINDOW_TYPE_NORMAL,
+                          shell_window_id);
+}
+
 display::Display AshTestImplMus::GetSecondaryDisplay() {
   return wm_test_base_->GetSecondaryDisplay();
 }
@@ -76,6 +85,20 @@ bool AshTestImplMus::SetSecondaryDisplayPlacement(
   return false;
 }
 
+void AshTestImplMus::ConfigureWidgetInitParamsForDisplay(
+    WmWindow* window,
+    views::Widget::InitParams* init_params) {
+  init_params
+      ->mus_properties[ui::mojom::WindowManager::kInitialDisplayId_Property] =
+      mojo::ConvertTo<std::vector<uint8_t>>(
+          WmWindowMus::GetMusWindow(window)->display_id());
+}
+
+void AshTestImplMus::AddTransientChild(WmWindow* parent, WmWindow* window) {
+  WmWindowMus::GetMusWindow(parent)->AddTransientWindow(
+      WmWindowMus::GetMusWindow(window));
+}
+
 }  // namespace mus
 
 // static
@@ -83,4 +106,9 @@ std::unique_ptr<AshTestImpl> AshTestImpl::Create() {
   return base::MakeUnique<mus::AshTestImplMus>();
 }
 
+// static
+bool AshTest::IsMash() {
+  return true;
+}
+
 }  // namespace ash