views/mus: Install a mus-friend ContextFactory for tests.

ui/aura/window_tree_host.cc

 // Copyright (c) 2013 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/window_tree_host.h"
 
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/cursor_client.h"
@@ skipping 231 matching lines @@
   // we ensure GetRootWindow() still returns this.
   //window()->RemoveOrDestroyChildren();
 }
 
 void WindowTreeHost::CreateCompositor(const cc::FrameSinkId& frame_sink_id) {
   DCHECK(Env::GetInstance());
   ui::ContextFactory* context_factory = Env::GetInstance()->context_factory();
   DCHECK(context_factory);
   ui::ContextFactoryPrivate* context_factory_private =
       Env::GetInstance()->context_factory_private();
-  compositor_.reset(new ui::Compositor(
-      frame_sink_id.is_valid() ? frame_sink_id
-                               : context_factory_private->AllocateFrameSinkId(),
-      context_factory, context_factory_private,
-      base::ThreadTaskRunnerHandle::Get()));
+  compositor_.reset(
+      new ui::Compositor((!context_factory_private || frame_sink_id.is_valid())
+                             ? frame_sink_id
+                             : context_factory_private->AllocateFrameSinkId(),
+                         context_factory, context_factory_private,
+                         base::ThreadTaskRunnerHandle::Get()));
   if (!dispatcher()) {
     window()->Init(ui::LAYER_NOT_DRAWN);
     window()->set_host(this);
     window()->SetName("RootWindow");
     dispatcher_.reset(new WindowEventDispatcher(this));
   }
 }
 
 void WindowTreeHost::InitCompositor() {
   compositor_->SetScaleAndSize(GetDeviceScaleFactorFromDisplay(window()),
@@ skipping 75 matching lines @@
   client::CursorClient* cursor_client = client::GetCursorClient(window());
   if (cursor_client) {
     const display::Display& display =
         display::Screen::GetScreen()->GetDisplayNearestWindow(window());
     cursor_client->SetDisplay(display);
   }
   dispatcher()->OnCursorMovedToRootLocation(root_location);
 }
 
 }  // namespace aura