[Sync] Don't commit items with predecessors/parents in conflict.

chrome/browser/sync/sessions/ordered_commit_set.cc

Index: chrome/browser/sync/sessions/ordered_commit_set.cc
diff --git a/chrome/browser/sync/sessions/ordered_commit_set.cc b/chrome/browser/sync/sessions/ordered_commit_set.cc
index d70049421e1ff3472c0017cf51d741271b7a72c3..3700e1c3eda62b81d58c6c16ae3cabfb96ddb072 100644
--- a/chrome/browser/sync/sessions/ordered_commit_set.cc
+++ b/chrome/browser/sync/sessions/ordered_commit_set.cc
@@ -31,6 +31,13 @@ void OrderedCommitSet::AddCommitItem(const int64 metahandle,
   }
 }
 
+void OrderedCommitSet::Append(const OrderedCommitSet& other) {
+  for (int i = 0; i < other.Size(); ++i) {
+    CommitItem item = other.GetCommitItemAt(i);
+    AddCommitItem(item.meta, item.id, item.group);
+  }
+}
+
 void OrderedCommitSet::AppendReverse(const OrderedCommitSet& other) {
   for (int i = other.Size() - 1; i >= 0; i--) {
     CommitItem item = other.GetCommitItemAt(i);