Unittest for fix to allow navigation when there is no history DB....

chrome/browser/history/history_backend.h

Index: chrome/browser/history/history_backend.h
===================================================================
--- chrome/browser/history/history_backend.h	(revision 30724)
+++ chrome/browser/history/history_backend.h	(working copy)
@@ -1,4 +1,4 @@
-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -99,7 +99,9 @@
   // Must be called after creation but before any objects are created. If this
   // fails, all other functions will fail as well. (Since this runs on another
   // thread, we don't bother returning failure.)
-  void Init();
+  //
+  // |force_fail| can be set during unittests to unconditionally fail to init.
+  void Init(bool force_fail);
 
   // Notification that the history system is shutting down. This will break
   // the refs owned by the delegate and any pending transaction so it will