ash: Use SessionController instead of SessionStateDelegate

ui/aura/mus/window_tree_client.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/aura/mus/window_tree_client.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 1589 matching lines @@
 void WindowTreeClient::SetFrameDecorationValues(
     ui::mojom::FrameDecorationValuesPtr values) {
   if (window_manager_internal_client_) {
     window_manager_internal_client_->WmSetFrameDecorationValues(
         std::move(values));
   }
 }
 
 void WindowTreeClient::SetNonClientCursor(Window* window,
                                           ui::mojom::Cursor cursor_id) {
-  window_manager_internal_client_->WmSetNonClientCursor(
-      WindowMus::Get(window)->server_id(), cursor_id);
+  if (window_manager_internal_client_) {
+    window_manager_internal_client_->WmSetNonClientCursor(
+        WindowMus::Get(window)->server_id(), cursor_id);
+  }
 }
 
 void WindowTreeClient::AddAccelerators(
     std::vector<ui::mojom::WmAcceleratorPtr> accelerators,
     const base::Callback<void(bool)>& callback) {
   if (window_manager_internal_client_) {
     window_manager_internal_client_->AddAccelerators(std::move(accelerators),
                                                      callback);
   }
 }
@@ skipping 242 matching lines @@
   return ScheduleInFlightChange(base::MakeUnique<InFlightCaptureChange>(
       this, capture_synchronizer_.get(), window));
 }
 
 uint32_t WindowTreeClient::CreateChangeIdForFocus(WindowMus* window) {
   return ScheduleInFlightChange(base::MakeUnique<InFlightFocusChange>(
       this, focus_synchronizer_.get(), window));
 }
 
 }  // namespace aura