[Sync] Make syncer commands avoid posting tasks on threads with no work to do

chrome/browser/sync/engine/build_and_process_conflict_sets_command.cc

Index: chrome/browser/sync/engine/build_and_process_conflict_sets_command.cc
diff --git a/chrome/browser/sync/engine/build_and_process_conflict_sets_command.cc b/chrome/browser/sync/engine/build_and_process_conflict_sets_command.cc
index 9810225b52b6a98c7ab28f0320f336906a4481c8..0a8cd8b3e32192c84257e4e2a79f648721f7b39a 100644
--- a/chrome/browser/sync/engine/build_and_process_conflict_sets_command.cc
+++ b/chrome/browser/sync/engine/build_and_process_conflict_sets_command.cc
@@ -30,6 +30,16 @@ using std::vector;
 BuildAndProcessConflictSetsCommand::BuildAndProcessConflictSetsCommand() {}
 BuildAndProcessConflictSetsCommand::~BuildAndProcessConflictSetsCommand() {}
 
+bool BuildAndProcessConflictSetsCommand::HasCustomGroupsToChange() const {
+  // TODO(akalin): Set to true.
+  return false;
+}
+
+std::set<ModelSafeGroup> BuildAndProcessConflictSetsCommand::GetGroupsToChange(
+    const sessions::SyncSession& session) const {
+  return session.GetEnabledGroupsWithConflicts();
+}
+
 void BuildAndProcessConflictSetsCommand::ModelChangingExecuteImpl(
     SyncSession* session) {
   session->mutable_status_controller()->update_conflict_sets_built(