Add the ability to unload the HistoryBackend....

chrome/browser/autocomplete/history_url_provider.cc

 // 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.
 
 #include "chrome/browser/autocomplete/history_url_provider.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/histogram.h"
@@ skipping 618 matching lines @@
     if (fixed_text.empty()) {
       // Conceivably fixup could result in an empty string (although I don't
       // have cases where this happens offhand).  We can't do anything with
       // empty input, so just bail; otherwise we'd crash later.
       return;
     }
     params->input.set_text(fixed_text);
 
     // Pass 1: Get the in-memory URL database, and use it to find and promote
     // the inline autocomplete match, if any.
-    history::URLDatabase* url_db = history_service->in_memory_database();
+    history::URLDatabase* url_db = history_service->InMemoryDatabase();
     // url_db can be NULL if it hasn't finished initializing (or failed to
     // initialize).  In this case all we can do is fall back on the second
-    // pass.  Ultimately, we should probably try to ensure the history system
-    // starts properly before we get here, as otherwise this can cause
-    // inconsistent behavior when the user has just started the browser and
-    // tries to type immediately.
+    // pass.
+    //
+    // TODO(pkasting): We should just block here until this loads.  Any time
+    // someone unloads the history backend, we'll get inconsistent inline
+    // autocomplete behavior here.
     if (url_db) {
       DoAutocomplete(NULL, url_db, params.get());
       // params->matches now has the matches we should expose to the provider.
       // Pass 2 expects a "clean slate" set of matches.
       matches_.clear();
       matches_.swap(params->matches);
       UpdateStarredStateOfMatches();
     }
   }
 
@@ skipping 169 matching lines @@
       history_match.input_location - offset, params->input.text().length(),
       match.contents.length(), ACMatchClassification::URL,
       &match.contents_class);
   match.description = info.title();
   AutocompleteMatch::ClassifyMatchInString(params->input.text(), info.title(),
                                            ACMatchClassification::NONE,
                                            &match.description_class);
 
   return match;
 }