aura: Some change to how the client-lib is set up.

ash/mus/window_manager_application.cc

Index: ash/mus/window_manager_application.cc
diff --git a/ash/mus/window_manager_application.cc b/ash/mus/window_manager_application.cc
index 9df9d531262eb63f791cebc81774a5bc43e16da3..a10a1ec7de1824d52bde6d2ab5d5f80c1fb403d1 100644
--- a/ash/mus/window_manager_application.cc
+++ b/ash/mus/window_manager_application.cc
@@ -27,9 +27,7 @@
 #include "services/service_manager/public/cpp/service_context.h"
 #include "services/tracing/public/cpp/provider.h"
 #include "services/ui/common/accelerator_util.h"
-#include "services/ui/public/cpp/gpu/gpu.h"
 #include "ui/aura/env.h"
-#include "ui/aura/mus/mus_context_factory.h"
 #include "ui/aura/mus/window_tree_client.h"
 #include "ui/events/event.h"
 #include "ui/message_center/message_center.h"
@@ -54,7 +52,6 @@ WindowManagerApplication::~WindowManagerApplication() {
     blocking_pool_->Shutdown(kMaxNewShutdownBlockingTasks);
   }
 
-  gpu_.reset();
   statistics_provider_.reset();
   ShutdownComponents();
 }
@@ -114,11 +111,6 @@ void WindowManagerApplication::OnStart() {
       context()->connector(), context()->identity(), "ash_mus_resources.pak",
       "ash_mus_resources_200.pak", nullptr,
       views::AuraInit::Mode::AURA_MUS_WINDOW_MANAGER);
-  gpu_ = ui::Gpu::Create(context()->connector());
-  compositor_context_factory_ =
-      base::MakeUnique<aura::MusContextFactory>(gpu_.get());
-  aura::Env::GetInstance()->set_context_factory(
-      compositor_context_factory_.get());
   window_manager_.reset(new WindowManager(context()->connector()));
 
   MaterialDesignController::Initialize();
@@ -127,7 +119,8 @@ void WindowManagerApplication::OnStart() {
 
   std::unique_ptr<aura::WindowTreeClient> window_tree_client =
       base::MakeUnique<aura::WindowTreeClient>(
-          context()->connector(), window_manager_.get(), window_manager_.get());
+          context()->connector(), nullptr /* io_task_runner */,
+          window_manager_.get(), window_manager_.get());
   window_tree_client->ConnectAsWindowManager();
 
   const size_t kMaxNumberThreads = 3u;  // Matches that of content.