Add support for converting cc::Region to and from protobuf.

cc/proto/cc_conversions.cc

+// Copyright 2015 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/proto/cc_conversions.h"
+
+#include "cc/base/region.h"
+#include "cc/proto/gfx_conversions.h"
+#include "cc/proto/region.pb.h"
+
+namespace cc {
+
+void RegionToProto(const Region& region, proto::Region* proto) {
+  for (Region::Iterator it(region); it.has_rect(); it.next())
+    RectToProto(it.rect(), proto->add_rects());
+}
+
+Region RegionFromProto(const proto::Region& proto) {
+  Region region;
+  for (int i = 0; i < proto.rects_size(); ++i)
+    region.Union(ProtoToRect(proto.rects(i)));
+  return region;
+}
+
+}  // namespace cc