Sync: ParentChildIndex fix for out of order deletion of entries by PurgeEntriesWithTypeIn.

sync/syncable/parent_child_index_unittest.cc

Index: sync/syncable/parent_child_index_unittest.cc
diff --git a/sync/syncable/parent_child_index_unittest.cc b/sync/syncable/parent_child_index_unittest.cc
index 6362242f2481c9a933c6da01d3817fc7327d9b41..f94c5b95b4215e17b2c7877d59a0eded7f089ff5 100644
--- a/sync/syncable/parent_child_index_unittest.cc
+++ b/sync/syncable/parent_child_index_unittest.cc
@@ -409,9 +409,45 @@ TEST_F(ParentChildIndexTest, NodesWithImplicitParentId) {
   EXPECT_FALSE(index_.Contains(p2));
   children = index_.GetChildren(type_root);
   ASSERT_EQ(nullptr, children);
+}
+
+// Test that the removal isn't sensitive to the order (PurgeEntriesWithTypeIn
+// removes items in arbitrary order).
+TEST_F(ParentChildIndexTest, RemoveOutOfOrder) {
+  // Insert a type root and two items (with implicit parent ID).
+  syncable::Id type_root_id = syncable::Id::CreateFromServerId("type_root");
+  EntryKernel* type_root = MakeTypeRoot(PREFERENCES, type_root_id);
+  index_.Insert(type_root);
+  EntryKernel* p1 = MakeUniqueClientItem(PREFERENCES, 1);
+  EntryKernel* p2 = MakeUniqueClientItem(PREFERENCES, 2);
+  index_.Insert(p1);
+  index_.Insert(p2);
 
+  // Two items expected under the type root.
+  const OrderedChildSet* children = index_.GetChildren(type_root);
+  ASSERT_TRUE(children);
+  EXPECT_EQ(2UL, children->size());
+
+  // Remove all 3 items in arbitrary order.
+  index_.Remove(p2);
   index_.Remove(type_root);
-  EXPECT_EQ(Id(), IndexKnownModelTypeRootId(PREFERENCES));
+  index_.Remove(p1);
+
+  EXPECT_EQ(nullptr, index_.GetChildren(type_root));
+
+  // Add a new root and another two items again.
+  type_root = MakeTypeRoot(PREFERENCES, type_root_id);
+  index_.Insert(type_root);
+
+  index_.Insert(MakeUniqueClientItem(PREFERENCES, 3));
+  index_.Insert(MakeUniqueClientItem(PREFERENCES, 4));
+
+  children = index_.GetChildren(type_root);
+  ASSERT_TRUE(children);
+  // Should have 2 items. If the out of order removal cleared the implicit
+  // parent folder ID prematurely, the collection would have 3 items including
+  // p1.
+  EXPECT_EQ(2UL, children->size());
 }
 
 }  // namespace syncable