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

chrome/browser/sync/engine/resolve_conflicts_command.cc

Index: chrome/browser/sync/engine/resolve_conflicts_command.cc
diff --git a/chrome/browser/sync/engine/resolve_conflicts_command.cc b/chrome/browser/sync/engine/resolve_conflicts_command.cc
index 7329da90dc481fbeb093111513c461f3df86e957..1338e2e372bff44f31887f515413318f041e8f8d 100644
--- a/chrome/browser/sync/engine/resolve_conflicts_command.cc
+++ b/chrome/browser/sync/engine/resolve_conflicts_command.cc
@@ -14,6 +14,11 @@ namespace browser_sync {
 ResolveConflictsCommand::ResolveConflictsCommand() {}
 ResolveConflictsCommand::~ResolveConflictsCommand() {}
 
+std::set<ModelSafeGroup> ResolveConflictsCommand::GetGroupsToChange(
+    const sessions::SyncSession& session) const {
+  return session.GetEnabledGroupsWithConflicts();
+}
+
 void ResolveConflictsCommand::ModelChangingExecuteImpl(
     sessions::SyncSession* session) {
   ConflictResolver* resolver = session->context()->resolver();