Add PlatformScreenDelegate and start implementation.

services/ui/ws/display_unittest.cc

 // Copyright 2016 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 <stdint.h>
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 44 matching lines @@
 
 class DisplayTest : public testing::Test {
  public:
   DisplayTest() : cursor_id_(0), platform_display_factory_(&cursor_id_) {}
   ~DisplayTest() override {}
 
  protected:
   // testing::Test:
   void SetUp() override {
     PlatformDisplay::set_factory_for_testing(&platform_display_factory_);
-    window_server_.reset(new WindowServer(&window_server_delegate_,
-                                          scoped_refptr<SurfacesState>()));
+    window_server_.reset(new WindowServer(&window_server_delegate_));
     window_server_delegate_.set_window_server(window_server_.get());
     window_server_->user_id_tracker()->AddUserId(kTestId1);
     window_server_->user_id_tracker()->AddUserId(kTestId2);
   }
 
  protected:
   int32_t cursor_id_;
   TestPlatformDisplayFactory platform_display_factory_;
   TestWindowServerDelegate window_server_delegate_;
   std::unique_ptr<WindowServer> window_server_;
@@ skipping 222 matching lines @@
   Display* display2 = tree->GetDisplay(root2);
   WindowManagerState* display2_wms =
       display2->GetWindowManagerDisplayRootForUser(kTestId1)
           ->window_manager_state();
   EXPECT_EQ(display1_wms->window_tree(), display2_wms->window_tree());
 }
 
 }  // namespace test
 }  // namespace ws
 }  // namespace ui