Revert 148792 - [Sync] Remove CleanupDisabledTypes command and move purge logic into SyncManager.

sync/engine/sync_scheduler_impl.h

Index: sync/engine/sync_scheduler_impl.h
===================================================================
--- sync/engine/sync_scheduler_impl.h	(revision 148811)
+++ sync/engine/sync_scheduler_impl.h	(working copy)
@@ -99,8 +99,12 @@
       // a sync.  The source is inferable from |session.source()|.
       NUDGE,
       // Typically used for fetching updates for a subset of the enabled types
-      // during initial sync or reconfiguration.
+      // during initial sync or reconfiguration.  We don't run all steps of
+      // the sync cycle for these (e.g. CleanupDisabledTypes is skipped).
       CONFIGURATION,
+      // The user disabled some types and we have to clean up the data
+      // for those.
+      CLEANUP_DISABLED_TYPES,
     };
     SyncSessionJob();
     SyncSessionJob(SyncSessionJobPurpose purpose, base::TimeTicks start,
@@ -216,6 +220,10 @@
   // reset our state.
   void FinishSyncSessionJob(const SyncSessionJob& job);
 
+  // Record important state that might be needed in future syncs, such as which
+  // data types may require cleanup.
+  void UpdateCarryoverSessionState(const SyncSessionJob& old_job);
+
   // Helper to FinishSyncSessionJob to schedule the next sync operation.
   void ScheduleNextSync(const SyncSessionJob& old_job);