Change cc::ElementId to be a uint64_t

cc/trees/element_id.cc

Index: cc/trees/element_id.cc
diff --git a/cc/trees/element_id.cc b/cc/trees/element_id.cc
index 45913303c1019dfa9c36113d6a11fffae12c1bfb..66c13566df4da0ace4530009e5db2c07212260b4 100644
--- a/cc/trees/element_id.cc
+++ b/cc/trees/element_id.cc
@@ -3,17 +3,15 @@
 // found in the LICENSE file.
 
 #include "cc/trees/element_id.h"
-
 #include <limits>
 #include <ostream>
-
 #include "base/trace_event/trace_event_argument.h"
 #include "base/values.h"
 
 namespace cc {
 
 bool ElementId::operator==(const ElementId& o) const {
-  return primaryId == o.primaryId && secondaryId == o.secondaryId;
+  return id == o.id;
 }
 
 bool ElementId::operator!=(const ElementId& o) const {
@@ -21,36 +19,15 @@ bool ElementId::operator!=(const ElementId& o) const {
 }
 
 bool ElementId::operator<(const ElementId& o) const {
-  return std::tie(primaryId, secondaryId) <
-         std::tie(o.primaryId, o.secondaryId);
+  return id < o.id;
 }
 
 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);
-}
-
-size_t ElementIdHash::operator()(ElementId key) const {
-  return base::HashInts(key.primaryId, key.secondaryId);
+  return !!id;
 }
 
-std::ostream& operator<<(std::ostream& out, const ElementId& id) {
-  return out << "(" << id.primaryId << ", " << id.secondaryId << ")";
+std::ostream& operator<<(std::ostream& out, const ElementId& element_id) {
+  return out << "(" << element_id.id << ")";
 }
 
 }  // namespace cc