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

chrome/browser/sync/engine/syncer_unittest.cc

Index: chrome/browser/sync/engine/syncer_unittest.cc
diff --git a/chrome/browser/sync/engine/syncer_unittest.cc b/chrome/browser/sync/engine/syncer_unittest.cc
index 582655eabe6ff97341330f4233b19824d6c12077..50c30fc8a29ea187d577b709dbb328a0eca7ff7b 100644
--- a/chrome/browser/sync/engine/syncer_unittest.cc
+++ b/chrome/browser/sync/engine/syncer_unittest.cc
@@ -2162,6 +2162,8 @@ TEST_F(SyncerTest, CommitsUpdateDoesntAlterEntry) {
 }
 
 TEST_F(SyncerTest, ParentAndChildBothMatch) {
+  syncable::ModelTypeBitSet all_types;
+  all_types.set();
   ScopedDirLookup dir(syncdb_.manager(), syncdb_.name());
   CHECK(dir.good());
   syncable::Id parent_id = ids_.NewServerId();
@@ -2198,7 +2200,7 @@ TEST_F(SyncerTest, ParentAndChildBothMatch) {
     dir->GetChildHandlesById(&trans, parent_id, &children);
     EXPECT_EQ(1u, children.size());
     Directory::UnappliedUpdateMetaHandles unapplied;
-    dir->GetUnappliedUpdateMetaHandles(&trans, &unapplied);
+    dir->GetUnappliedUpdateMetaHandles(&trans, all_types, &unapplied);
     EXPECT_EQ(0u, unapplied.size());
     syncable::Directory::UnsyncedMetaHandles unsynced;
     dir->GetUnsyncedMetaHandles(&trans, &unsynced);