Make sure we can still navigate to URLs when the History DB can't be loaded....

chrome/browser/autocomplete/history_url_provider.h

 // Copyright (c) 2006-2008 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.
 
 #ifndef CHROME_BROWSER_AUTOCOMPLETE_HISTORY_URL_PROVIDER_H_
 #define CHROME_BROWSER_AUTOCOMPLETE_HISTORY_URL_PROVIDER_H_
 
 #include <vector>
 #include <deque>
 
@@ skipping 83 matching lines @@
   // Set when "http://" should be trimmed from the beginning of the URLs.
   bool trim_http;
 
   // Set by the main thread to cancel this request. READ ONLY when running in
   // ExecuteWithDB() on the history thread to prevent deadlock. If this flag is
   // set when the query runs, the query will be abandoned. This allows us to
   // avoid running queries that are no longer needed. Since we don't care if
   // we run the extra queries, the lack of signaling is not a problem.
   bool cancel;
 
+  // Set by ExecuteWithDB() on the history thread when the query could not be
+  // performed because the history system failed to properly init the database.
+  // If this is set when the main thread is called back, it avoids changing
+  // |matches_| at all, so it won't delete the default match
+  // RunAutocompletePasses() creates.
+  bool failed;
+
   // List of matches written by the history thread.  We keep this separate list
   // to avoid having the main thread read the provider's matches while the
   // history thread is manipulating them.  The provider copies this list back
   // to matches_ on the main thread in QueryComplete().
   ACMatches matches;
 
   // Languages we should pass to gfx::GetCleanStringFromUrl.
   std::wstring languages;
 
  private:
@@ skipping 264 matching lines @@
   const Prefixes prefixes_;
 
   // Params for the current query.  The provider should not free this directly;
   // instead, it is passed as a parameter through the history backend, and the
   // parameter itself is freed once it's no longer needed.  The only reason we
   // keep this member is so we can set the cancel bit on it.
   HistoryURLProviderParams* params_;
 };
 
 #endif  // CHROME_BROWSER_AUTOCOMPLETE_HISTORY_URL_PROVIDER_H_