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..ddc7548cd456d0cafbe7a4d73952b06ff1c975e8
--- /dev/null
+++ b/cc/animation/element_id.cc
@@ -0,0 +1,52 @@
+// 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 CC_EXPORT operator==(uint64_t o, const ElementId& e) {
+  return o == e.value;
+}
+
+bool CC_EXPORT operator!=(uint64_t o, const ElementId& e) {
+  return o != e.value;
+}
+
+ElementId CC_EXPORT LayerIdToElementIdForTesting(int layer_id) {
+  return ElementId(std::numeric_limits<uint64_t>::max() - layer_id);
+}
+
+void ElementId::AddToTracedValue(base::trace_event::TracedValue* res) const {
+  res->SetInteger("element_id", base::saturated_cast<int>(value));
+  res->SetInteger("sub_element_id", base::saturated_cast<int>(value >> 32));
+}
+
+std::unique_ptr<base::Value> ElementId::AsValue() const {
+  std::unique_ptr<base::DictionaryValue> res(new base::DictionaryValue());
+  res->SetInteger("element_id", base::saturated_cast<int>(value));
+  res->SetInteger("sub_element_id", base::saturated_cast<int>(value >> 32));
+  return std::move(res);
+}
+
+void ElementId::ToProtobuf(proto::ElementId* proto) const {
+  proto->set_id(value);
+}
+
+void ElementId::FromProtobuf(const proto::ElementId& proto) {
+  value = proto.id();
+}
+
+std::ostream& operator<<(std::ostream& out, const ElementId& id) {
+  return out << id.value;
+}
+
+}  // namespace cc