views/mus: WindowTreeHostMus doesn't need to know about SurfaceType.

ui/views/mus/native_widget_mus.cc

 // Copyright 2015 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/views/mus/native_widget_mus.h"
 
 #include "base/macros.h"
 #include "base/thread_task_runner_handle.h"
 #include "components/mus/public/cpp/property_type_converters.h"
 #include "components/mus/public/cpp/window.h"
@@ skipping 289 matching lines @@
   // For Chrome, we need the GpuProcessTransportFactory so that renderer and
   // browser pixels are composited into a single backing
   // SoftwareOutputDeviceMus.
   if (!default_context_factory) {
     if (!context_factory_) {
       context_factory_.reset(new SurfaceContextFactory(shell_, window_,
                                                        surface_type_));
     }
     aura::Env::GetInstance()->set_context_factory(context_factory_.get());
   }
-  window_tree_host_.reset(
-      new WindowTreeHostMus(shell_, this, window_, surface_type_));
+  window_tree_host_.reset(new WindowTreeHostMus(shell_, this, window_));
   window_tree_host_->AddObserver(this);
   window_tree_host_->InitHost();
   aura::Env::GetInstance()->set_context_factory(default_context_factory);
   window_tree_host_->window()->SetProperty(kMusWindow, window_);
 
   focus_client_.reset(new wm::FocusController(new FocusRulesImpl));
 
   aura::client::SetFocusClient(window_tree_host_->window(),
                                focus_client_.get());
   aura::client::SetActivationClient(window_tree_host_->window(),
@@ skipping 527 matching lines @@
 
 void NativeWidgetMus::OnGestureEvent(ui::GestureEvent* event) {
   native_widget_delegate_->OnGestureEvent(event);
 }
 
 void NativeWidgetMus::OnHostCloseRequested(const aura::WindowTreeHost* host) {
   GetWidget()->Close();
 }
 
 }  // namespace views