Sync: Change Local IDs to GUID based to avoid ID collision

sync/syncable/in_memory_directory_backing_store.h

Index: sync/syncable/in_memory_directory_backing_store.h
diff --git a/sync/syncable/in_memory_directory_backing_store.h b/sync/syncable/in_memory_directory_backing_store.h
index d22e65fc53eb09866bdcb19e33679916de174926..ff858705ae6550b46ce7782933c4ee1de5a8b680 100644
--- a/sync/syncable/in_memory_directory_backing_store.h
+++ b/sync/syncable/in_memory_directory_backing_store.h
@@ -29,13 +29,7 @@ class SYNC_EXPORT_PRIVATE InMemoryDirectoryBackingStore
                      MetahandleSet* metahandles_to_purge,
                      Directory::KernelLoadInfo* kernel_load_info) override;
 
-  void request_consistent_cache_guid() {
-    consistent_cache_guid_requested_ = true;
-  }
-
  private:
-  bool consistent_cache_guid_requested_;
-
   DISALLOW_COPY_AND_ASSIGN(InMemoryDirectoryBackingStore);
 };