sync: Per-type update application

sync/syncable/directory.h

Index: sync/syncable/directory.h
diff --git a/sync/syncable/directory.h b/sync/syncable/directory.h
index 7a58dfc21c77aa2e82297253b4b71bf522514d8a..0206dbb458b5acc8ed32d0cd8c4ecde1f1f78363 100644
--- a/sync/syncable/directory.h
+++ b/sync/syncable/directory.h
@@ -315,11 +315,8 @@ class SYNC_EXPORT Directory {
   void GetUnsyncedMetaHandles(BaseTransaction* trans,
                               Metahandles* result);
 
-  // Returns all server types with unapplied updates.  A subset of
-  // those types can then be passed into
-  // GetUnappliedUpdateMetaHandles() below.
-  FullModelTypeSet GetServerTypesWithUnappliedUpdates(
-      BaseTransaction* trans) const;
+  // Returns whether or not this |type| has unapplied updates.
+  bool TypeHasUnappliedUpdates(ModelType type);
 
   // Get all the metahandles for unapplied updates for a given set of
   // server types.