Some history backend fixes for database corruption.

chrome/browser/history/history_backend.cc

 // Copyright (c) 2009 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/history/history_backend.h"
 
 #include <set>
 
 #include "base/compiler_specific.h"
 #include "base/file_util.h"
@@ skipping 230 matching lines @@
 
 FilePath HistoryBackend::GetThumbnailFileName() const {
   return history_dir_.Append(chrome::kThumbnailsFilename);
 }
 
 FilePath HistoryBackend::GetArchivedFileName() const {
   return history_dir_.Append(chrome::kArchivedHistoryFilename);
 }
 
 SegmentID HistoryBackend::GetLastSegmentID(VisitID from_visit) {
+  // Set is used to detect referrer loops.  Should not happen, but can
+  // if the database is corrupt.
+  std::set<VisitID> visit_set;
   VisitID visit_id = from_visit;
   while (visit_id) {
     VisitRow row;
     if (!db_->GetRowForVisit(visit_id, &row))
       return 0;
     if (row.segment_id)
       return row.segment_id;  // Found a visit in this change with a segment.
 
     // Check the referrer of this visit, if any.
     visit_id = row.referring_visit;
+
+    if (visit_set.find(visit_id) != visit_set.end()) {
+      NOTREACHED() << "Loop in referer chain, giving up";
+      break;
+    }
+    visit_set.insert(visit_id);
   }
   return 0;
 }
 
 SegmentID HistoryBackend::UpdateSegments(const GURL& url,
                                          VisitID from_visit,
                                          VisitID visit_id,
                                          PageTransition::Type transition_type,
                                          const Time ts) {
   if (!db_.get())
@@ skipping 1697 matching lines @@
   return true;
 }
 
 BookmarkService* HistoryBackend::GetBookmarkService() {
   if (bookmark_service_)
     bookmark_service_->BlockTillLoaded();
   return bookmark_service_;
 }
 
 }  // namespace history