Omnibox: Clobber HQP Cache File when user mucks with history

chrome/browser/history/in_memory_url_index.cc

 // Copyright (c) 2012 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/in_memory_url_index.h"
 
 #include "base/debug/trace_event.h"
 #include "base/file_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
@@ skipping 220 matching lines @@
 
 void InMemoryURLIndex::OnURLsDeleted(const URLsDeletedDetails* details) {
   if (details->all_history) {
     ClearPrivateData();
     needs_to_be_cached_ = true;
   } else {
     for (URLRows::const_iterator row = details->rows.begin();
          row != details->rows.end(); ++row)
       needs_to_be_cached_ |= private_data_->DeleteURL(row->url());
   }
+  // If we made changes, destroy the previous cache.  Otherwise, if we go
+  // through an unclean shutdown (and therefore fail to write a new cache file),
+  // when Chrome restarts and we restore from the previous cache, we'll end up
+  // searching over URLs that may be deleted.  This would be wrong, and
+  // surprising to the user who bothered to delete some URLs from his/her
+  // history.  In this situation, deleting the cache is a better solution than
+  // writing a new cache (after deleting the URLs from the in-memory structure)
+  // because deleting the cache forces it to be rebuilt from history upon
+  // startup.  If we instead write a new, updated cache then at the time of next
+  // startup (after an unclean shutdown) we will not rebuild the in-memory data
+  // structures from history but rather use the cache.  This solution is
+  // mediocre because this cache may not have the most-recently-visited URLs
+  // in it (URLs visited after user deleted some URLs from history), which
+  // would be odd and confusing.  It's better to force a rebuild.
+  base::FilePath path;
+  if (needs_to_be_cached_ && GetCacheFilePath(&path)) {
+    content::BrowserThread::PostBlockingPoolTask(
+        FROM_HERE, base::Bind(DeleteCacheFile, path));
+  }
 }
 
 // Restoring from Cache --------------------------------------------------------
 
 void InMemoryURLIndex::PostRestoreFromCacheFileTask() {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   TRACE_EVENT0("browser", "InMemoryURLIndex::PostRestoreFromCacheFileTask");
 
   base::FilePath path;
   if (!GetCacheFilePath(&path) || shutdown_) {
@@ skipping 101 matching lines @@
         base::Bind(DeleteCacheFile, path));
   }
 }
 
 void InMemoryURLIndex::OnCacheSaveDone(bool succeeded) {
   if (save_cache_observer_)
     save_cache_observer_->OnCacheSaveFinished(succeeded);
 }
 
 }  // namespace history