cros: Adds ShellPort functions for simplified display mode

ash/host/ash_window_tree_host.cc

Index: ash/host/ash_window_tree_host.cc
diff --git a/ash/host/ash_window_tree_host.cc b/ash/host/ash_window_tree_host.cc
index 939f097d35648af36c2c33d1b4c972f8e1cb175b..31cdd01be556ab41b2d0eba6930a9594b9e28c57 100644
--- a/ash/host/ash_window_tree_host.cc
+++ b/ash/host/ash_window_tree_host.cc
@@ -6,6 +6,8 @@
 
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/ash_window_tree_host_unified.h"
+#include "ash/shell_port.h"
+#include "base/memory/ptr_util.h"
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/events/event.h"
@@ -21,6 +23,8 @@ namespace ash {
 
 AshWindowTreeHost::AshWindowTreeHost() : input_method_handler_(nullptr) {}
 
+AshWindowTreeHost::~AshWindowTreeHost() = default;
+
 void AshWindowTreeHost::TranslateLocatedEvent(ui::LocatedEvent* event) {
   if (event->IsTouchEvent())
     return;
@@ -47,14 +51,22 @@ void AshWindowTreeHost::TranslateLocatedEvent(ui::LocatedEvent* event) {
 }
 
 // static
-AshWindowTreeHost* AshWindowTreeHost::Create(
+std::unique_ptr<AshWindowTreeHost> AshWindowTreeHost::Create(
     const AshWindowTreeHostInitParams& init_params) {
-  if (init_params.offscreen)
-    return new AshWindowTreeHostUnified(init_params.initial_bounds);
+  std::unique_ptr<AshWindowTreeHost> ash_window_tree_host =
+      ShellPort::Get()->CreateAshWindowTreeHost(init_params);
+  if (ash_window_tree_host)
+    return ash_window_tree_host;
+
+  if (init_params.offscreen) {
+    return base::MakeUnique<AshWindowTreeHostUnified>(
+        init_params.initial_bounds);
+  }
 #if defined(USE_OZONE)
-  return new AshWindowTreeHostPlatform(init_params.initial_bounds);
+  return base::MakeUnique<AshWindowTreeHostPlatform>(
+      init_params.initial_bounds);
 #elif defined(USE_X11)
-  return new AshWindowTreeHostX11(init_params.initial_bounds);
+  return base::MakeUnique<AshWindowTreeHostX11>(init_params.initial_bounds);
 #else
 #error Unsupported platform.
 #endif