[Sync] Move snapshot cache from SBHI to PSS.

components/sync/engine/fake_sync_engine.cc

Index: components/sync/engine/fake_sync_engine.cc
diff --git a/components/sync/engine/fake_sync_engine.cc b/components/sync/engine/fake_sync_engine.cc
index 284b3b1b47546d4a1956a2ae094cf990273372f2..e40e6739ad0ec040512e75df3e0d6fcb829f72cd 100644
--- a/components/sync/engine/fake_sync_engine.cc
+++ b/components/sync/engine/fake_sync_engine.cc
@@ -61,10 +61,6 @@ SyncEngine::Status FakeSyncEngine::GetDetailedStatus() {
   return SyncEngine::Status();
 }
 
-SyncCycleSnapshot FakeSyncEngine::GetLastCycleSnapshot() const {
-  return SyncCycleSnapshot();
-}
-
 bool FakeSyncEngine::HasUnsyncedItems() const {
   return false;
 }