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

chrome/browser/predictors/predictor_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/predictors/predictor_database.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
@@ skipping 52 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(PredictorDatabaseInternal);
 };
 
 
 PredictorDatabaseInternal::PredictorDatabaseInternal(Profile* profile)
     : db_path_(profile->GetPath().Append(kPredictorDatabaseName)),
       db_(new sql::Connection()),
       autocomplete_table_(new AutocompleteActionPredictorTable()),
       resource_prefetch_tables_(new ResourcePrefetchPredictorTables()) {
   db_->set_histogram_tag("Predictor");
+
+  // 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();
+
   ResourcePrefetchPredictorConfig config;
   is_resource_prefetch_predictor_enabled_ =
       IsSpeculativeResourcePrefetchingEnabled(profile, &config);
 }
 
 PredictorDatabaseInternal::~PredictorDatabaseInternal() {
   // The connection pointer needs to be deleted on the DB thread since there
   // might be a task in progress on the DB thread which uses this connection.
   if (BrowserThread::IsMessageLoopValid(BrowserThread::DB))
     BrowserThread::DeleteSoon(BrowserThread::DB, FROM_HERE, db_.release());
@@ skipping 63 matching lines @@
 scoped_refptr<ResourcePrefetchPredictorTables>
     PredictorDatabase::resource_prefetch_tables() {
   return db_->resource_prefetch_tables_;
 }
 
 sql::Connection* PredictorDatabase::GetDatabase() {
   return db_->db_.get();
 }
 
 }  // namespace predictors