cc: Add SwapPromiseManager and SurfaceSequenceGenerator.

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