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

chrome/browser/sync/sessions/ordered_commit_set.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/sync/sessions/ordered_commit_set.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 
@@ skipping 13 matching lines @@
   if (!HaveCommitItem(metahandle)) {
     inserted_metahandles_.insert(metahandle);
     metahandle_order_.push_back(metahandle);
     commit_ids_.push_back(commit_id);
     projections_[GetGroupForModelType(type, routes_)].push_back(
         commit_ids_.size() - 1);
     types_.push_back(type);
   }
 }
 
+void OrderedCommitSet::Clear() {
+  inserted_metahandles_.clear();
+  metahandle_order_.clear();
+  commit_ids_.clear();
+  projections_.clear();
+  types_.clear();
+}
+
 void OrderedCommitSet::AppendReverse(const OrderedCommitSet& other) {
   for (int i = other.Size() - 1; i >= 0; i--) {
     CommitItem item = other.GetCommitItemAt(i);
     AddCommitItem(item.meta, item.id, item.group);
   }
 }
 
 void OrderedCommitSet::Truncate(size_t max_size) {
   if (max_size < metahandle_order_.size()) {
     for (size_t i = max_size; i < metahandle_order_.size(); ++i) {
@@ skipping 50 matching lines @@
   commit_ids_ = other.commit_ids_;
   metahandle_order_ = other.metahandle_order_;
   projections_ = other.projections_;
   types_ = other.types_;
   routes_ = other.routes_;
 }
 
 }  // namespace sessions
 }  // namespace browser_sync