[sync] Verify existence of the root when loading DirectoryBackingStore

components/sync/syncable/directory_backing_store.cc

Index: components/sync/syncable/directory_backing_store.cc
diff --git a/components/sync/syncable/directory_backing_store.cc b/components/sync/syncable/directory_backing_store.cc
index b17ff27522c08c7659bf0c44585193f1cd4dfe93..05414bf324ac6e0c93ff372c28c276c5c2690b81 100644
--- a/components/sync/syncable/directory_backing_store.cc
+++ b/components/sync/syncable/directory_backing_store.cc
@@ -1642,6 +1642,7 @@ bool DirectoryBackingStore::CreateShareInfoTableVersion71(
 
 // This function checks to see if the given list of Metahandles has any nodes
 // whose PARENT_ID values refer to ID values that do not actually exist.
+// This function also checks that the root node exists in the set.

[pavely, 2016/09/15 22:50:15]

I would say "that root node with correct id exists...".

 // Returns true on success.
 bool DirectoryBackingStore::VerifyReferenceIntegrity(
     const Directory::MetahandlesMap* handles_map) {
@@ -1667,6 +1668,9 @@ bool DirectoryBackingStore::VerifyReferenceIntegrity(
       }
     }
   }
+  if (ids_set.find(Id::GetRoot().value()) == ids_set.end()) {

[pavely, 2016/09/15 22:50:15]

nit: Since you are using Id class directly could you include syncable_id.h

+    return false;
+  }
   return is_ok;
 }