cros: Adds ShellPort functions for simplified display mode

ash/aura/shell_port_classic.cc

Index: ash/aura/shell_port_classic.cc
diff --git a/ash/aura/shell_port_classic.cc b/ash/aura/shell_port_classic.cc
index 9d87e869ec42fc806c881927be458698d84534f7..fa3cb150f44f6c30fd5f2809489d26847a1a7625 100644
--- a/ash/aura/shell_port_classic.cc
+++ b/ash/aura/shell_port_classic.cc
@@ -44,6 +44,8 @@
 
 #if defined(USE_OZONE)
 #include "ash/wm/maximize_mode/scoped_disable_internal_mouse_and_keyboard_ozone.h"
+#include "ui/display/types/native_display_delegate.h"
+#include "ui/ozone/public/ozone_platform.h"
 #endif
 
 namespace ash {
@@ -239,6 +241,12 @@ void ShellPortClassic::CreatePointerWatcherAdapter() {
   pointer_watcher_adapter_ = base::MakeUnique<PointerWatcherAdapter>();
 }
 
+AshWindowTreeHost* ShellPortClassic::CreateAshWindowTreeHost(
+    const AshWindowTreeHostInitParams& init_params) {
+  // A return value of null results in falling back to the default.
+  return nullptr;
+}
+
 void ShellPortClassic::CreatePrimaryHost() {
   Shell::Get()->window_tree_host_manager()->Start();
   AshWindowTreeHostInitParams ash_init_params;
@@ -249,6 +257,11 @@ void ShellPortClassic::InitHosts(const ShellInitParams& init_params) {
   Shell::Get()->window_tree_host_manager()->InitHosts();
 }
 
+std::unique_ptr<display::NativeDisplayDelegate>
+ShellPortClassic::CreateNativeDisplayDelegate() {
+  return ui::OzonePlatform::GetInstance()->CreateNativeDisplayDelegate();
+}
+
 std::unique_ptr<AcceleratorController>
 ShellPortClassic::CreateAcceleratorController() {
   DCHECK(!accelerator_controller_delegate_);