WIP: Propagate SurfaceID up window tree hierarchy

cc/trees/surface_sequence_generator.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 <cc/trees/surface_sequence_generator.h>
-#include "cc/surfaces/surface_sequence.h"
-
-namespace cc {
-
-SurfaceSequenceGenerator::SurfaceSequenceGenerator()
-    : surface_client_id_(0u), next_surface_sequence_(1u) {}
-
-SurfaceSequenceGenerator::~SurfaceSequenceGenerator() = default;
-
-SurfaceSequence SurfaceSequenceGenerator::CreateSurfaceSequence() {
-  return SurfaceSequence(surface_client_id_, next_surface_sequence_++);
-}
-
-}  // namespace cc