Add GetSurfaceManager to ui::ContextFactory.

ash/mus/stub_context_factory.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 "ash/mus/stub_context_factory.h"
 
 #include "base/memory/ptr_util.h"
 #include "cc/output/context_provider.h"
 #include "cc/raster/single_thread_task_graph_runner.h"
 #include "cc/surfaces/surface_id_allocator.h"
@@ skipping 59 matching lines @@
 cc::TaskGraphRunner* StubContextFactory::GetTaskGraphRunner() {
   return task_graph_runner_.get();
 }
 
 std::unique_ptr<cc::SurfaceIdAllocator>
 StubContextFactory::CreateSurfaceIdAllocator() {
   return base::WrapUnique(
       new cc::SurfaceIdAllocator(next_surface_id_namespace_++));
 }
 
+cc::SurfaceManager* StubContextFactory::GetSurfaceManager() {
+  // NOTIMPLEMENTED();
+  return nullptr;
+}
+
 void StubContextFactory::ResizeDisplay(ui::Compositor* compositor,
                                        const gfx::Size& size) {}
 
 }  // namespace sysui
 }  // namespace ash