Use element id's for animations

cc/animation/element_id.cc

Index: cc/animation/element_id.cc
diff --git a/cc/animation/element_id.cc b/cc/animation/element_id.cc
new file mode 100644
index 0000000000000000000000000000000000000000..242cd32e621e37a9fb844d567dbc0f0a1c026410
--- /dev/null
+++ b/cc/animation/element_id.cc
@@ -0,0 +1,67 @@
+// 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/animation/element_id.h"
+
+#include <limits>
+#include <ostream>
+
+#include "base/trace_event/trace_event_argument.h"
+#include "base/values.h"
+#include "cc/proto/element_id.pb.h"
+
+namespace cc {
+
+bool ElementId::operator==(const ElementId& o) const {
+  return primaryId == o.primaryId && secondaryId == o.secondaryId;
+}
+
+bool ElementId::operator!=(const ElementId& o) const {
+  return !(*this == o);
+}
+
+bool ElementId::operator<(const ElementId& o) const {
+  return std::tie(primaryId, secondaryId) <
+         std::tie(o.primaryId, o.secondaryId);
+}
+
+ElementId::operator bool() const {
+  return !!primaryId;
+}
+
+ElementId LayerIdToElementIdForTesting(int layer_id) {
+  return ElementId(std::numeric_limits<int>::max() - layer_id, 0);
+}
+
+void ElementId::AddToTracedValue(base::trace_event::TracedValue* res) const {
+  res->SetInteger("primaryId", primaryId);
+  res->SetInteger("secondaryId", secondaryId);
+}
+
+std::unique_ptr<base::Value> ElementId::AsValue() const {
+  std::unique_ptr<base::DictionaryValue> res(new base::DictionaryValue());
+  res->SetInteger("primaryId", primaryId);
+  res->SetInteger("secondaryId", secondaryId);
+  return std::move(res);
+}
+
+void ElementId::ToProtobuf(proto::ElementId* proto) const {
+  proto->set_primary_id(primaryId);
+  proto->set_secondary_id(secondaryId);
+}
+
+void ElementId::FromProtobuf(const proto::ElementId& proto) {
+  primaryId = proto.primary_id();
+  secondaryId = proto.secondary_id();
+}
+
+size_t ElementIdHash::operator()(ElementId key) const {
+  return base::HashInts(key.primaryId, key.secondaryId);
+}
+
+std::ostream& operator<<(std::ostream& out, const ElementId& id) {
+  return out << "(" << id.primaryId << ", " << id.secondaryId << ")";
+}
+
+}  // namespace cc