[sql] Consider fresh databases suitable for memory-mapped I/O.

chrome/browser/extensions/activity_log/activity_database.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/extensions/activity_log/activity_database.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 48 matching lines @@
   did_init_ = true;
   if (BrowserThread::IsMessageLoopValid(BrowserThread::DB))
     DCHECK_CURRENTLY_ON(BrowserThread::DB);
   db_.set_histogram_tag("Activity");
   db_.set_error_callback(
       base::Bind(&ActivityDatabase::DatabaseErrorCallback,
                  base::Unretained(this)));
   db_.set_page_size(4096);
   db_.set_cache_size(32);
 
+  // TODO(shess): The current mitigation for http://crbug.com/537742 stores
+  // state in the meta table, which this database does not use.
+  db_.set_mmap_disabled();
+
   if (!db_.Open(db_name)) {
     LOG(ERROR) << db_.GetErrorMessage();
     return LogInitFailure();
   }
 
   // Wrap the initialization in a transaction so that the db doesn't
   // get corrupted if init fails/crashes.
   sql::Transaction committer(&db_);
   if (!committer.Begin())
     return LogInitFailure();
@@ skipping 151 matching lines @@
              field_types[i]);
         if (!db->Execute(table_updater.c_str()))
           return false;
       }
     }
   }
   return true;
 }
 
 }  // namespace extensions