First-time sync: asymptotic running time improvement

chrome/browser/sync/syncable/syncable_id.cc

Index: chrome/browser/sync/syncable/syncable_id.cc
diff --git a/chrome/browser/sync/syncable/syncable_id.cc b/chrome/browser/sync/syncable/syncable_id.cc
index 766289b176637a56365bad2536de27b844ea0870..eeefd59581a52588fd0cc8760b0a46ae0f62ba99 100644
--- a/chrome/browser/sync/syncable/syncable_id.cc
+++ b/chrome/browser/sync/syncable/syncable_id.cc
@@ -45,4 +45,19 @@ Id Id::CreateFromClientString(const string& local_id) {
   return id;
 }
 
+Id Id::GetLexicographicSuccessor() const {
+  // The successor of a string is given by appending the least
+  // character in the alphabet.
+  Id id = *this;
+  id.s_.push_back(std::numeric_limits<std::string::value_type>::min());
+  return id;
+}
+
+// static
+Id Id::GetLeastIdForLexicographicComparison() {
+  Id id;
+  id.s_.clear();
+  return id;
+}
+
 }  // namespace syncable