[Sync] Have SBH tell SyncManager which types to purge

chrome/browser/sync/glue/sync_backend_registrar.cc

Index: chrome/browser/sync/glue/sync_backend_registrar.cc
diff --git a/chrome/browser/sync/glue/sync_backend_registrar.cc b/chrome/browser/sync/glue/sync_backend_registrar.cc
index 5d99b0d25404645718eefb7ecc2626ee0014fdfa..69898b14c652b80693db61fa8942ba85412af680 100644
--- a/chrome/browser/sync/glue/sync_backend_registrar.cc
+++ b/chrome/browser/sync/glue/sync_backend_registrar.cc
@@ -85,6 +85,11 @@ SyncBackendRegistrar::SyncBackendRegistrar(
   }
 }
 
+SyncBackendRegistrar::~SyncBackendRegistrar() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(stopped_on_ui_thread_);
+}
+
 void SyncBackendRegistrar::SetInitialTypes(syncer::ModelTypeSet initial_types) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   base::AutoLock lock(lock_);
@@ -112,11 +117,8 @@ void SyncBackendRegistrar::SetInitialTypes(syncer::ModelTypeSet initial_types) {
         << "Password store not initialized, cannot sync passwords";
     routing_info_.erase(syncer::PASSWORDS);
   }
-}
 
-SyncBackendRegistrar::~SyncBackendRegistrar() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK(stopped_on_ui_thread_);
+  last_configured_types_ = syncer::GetRoutingInfoTypes(routing_info_);
 }
 
 bool SyncBackendRegistrar::IsNigoriEnabled() const {
@@ -165,10 +167,15 @@ syncer::ModelTypeSet SyncBackendRegistrar::ConfigureDataTypes(
            << syncer::ModelTypeSetToString(types_to_remove)
            << " to get new routing info "
            <<syncer::ModelSafeRoutingInfoToString(routing_info_);
+  last_configured_types_ = syncer::GetRoutingInfoTypes(routing_info_);
 
   return newly_added_types;
 }
 
+syncer::ModelTypeSet SyncBackendRegistrar::GetLastConfiguredTypes() const {
+  return last_configured_types_;
+}
+
 void SyncBackendRegistrar::StopOnUIThread() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(!stopped_on_ui_thread_);