mus/views: Fix creating gfx::Display in high-dpi.

ui/aura/test/aura_test_helper.cc

 // Copyright (c) 2012 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/test/aura_test_helper.h"
 
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "ui/aura/client/default_capture_client.h"
 #include "ui/aura/client/focus_client.h"
@@ skipping 49 matching lines @@
     env_ = aura::Env::CreateInstance();
   Env::GetInstance()->set_context_factory(context_factory);
   // Unit tests generally don't want to query the system, rather use the state
   // from RootWindow.
   EnvTestHelper env_helper(Env::GetInstance());
   env_helper.SetInputStateLookup(nullptr);
   env_helper.ResetEventState();
 
   ui::InitializeInputMethodForTesting();
 
-  gfx::Size host_size(800, 600);
+  gfx::Screen* screen = gfx::Screen::GetScreen();
+  gfx::Size host_size(screen ? screen->GetPrimaryDisplay().GetSizeInPixel()
+                             : gfx::Size(800, 600));
   test_screen_.reset(TestScreen::Create(host_size));
-  gfx::Screen::SetScreenInstance(test_screen_.get());
+  if (!screen)
+    gfx::Screen::SetScreenInstance(test_screen_.get());
   host_.reset(test_screen_->CreateHostForPrimaryDisplay());
 
   focus_client_.reset(new TestFocusClient);
   client::SetFocusClient(root_window(), focus_client_.get());
   stacking_client_.reset(new TestWindowTreeClient(root_window()));
   capture_client_.reset(new client::DefaultCaptureClient(root_window()));
 
   root_window()->Show();
   // Ensure width != height so tests won't confuse them.
   host()->SetBounds(gfx::Rect(host_size));
@@ skipping 22 matching lines @@
 
 void AuraTestHelper::RunAllPendingInMessageLoop() {
   // TODO(jbates) crbug.com/134753 Find quitters of this RunLoop and have them
   //              use run_loop.QuitClosure().
   base::RunLoop run_loop;
   run_loop.RunUntilIdle();
 }
 
 }  // namespace test
 }  // namespace aura