[sql] Use memory-mapped I/O for sql::Connection.

sql/statement.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 "sql/statement.h"
 
 #include "base/logging.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "third_party/sqlite/sqlite3.h"
@@ skipping 92 matching lines @@
 
     // StepInternal() cannot track success because statements may be reset
     // before reaching SQLITE_DONE.  Don't call CheckError() because
     // sqlite3_reset() returns the last step error, which StepInternal() already
     // checked.
     const int rc =sqlite3_reset(ref_->stmt());
     if (rc == SQLITE_OK && ref_->connection())
       ref_->connection()->RecordOneEvent(Connection::EVENT_STATEMENT_SUCCESS);
   }
 
+  // Potentially release dirty cache pages if an autocommit statement made
+  // changes.
+  if (ref_->connection())
+    ref_->connection()->ReleaseCacheMemoryIfNeeded(false);
+
   succeeded_ = false;
   stepped_ = false;
 }
 
 bool Statement::Succeeded() const {
   if (!is_valid())
     return false;
 
   return succeeded_;
 }
@@ skipping 226 matching lines @@
 
 int Statement::CheckError(int err) {
   // Please don't add DCHECKs here, OnSqliteError() already has them.
   succeeded_ = (err == SQLITE_OK || err == SQLITE_ROW || err == SQLITE_DONE);
   if (!succeeded_ && ref_.get() && ref_->connection())
     return ref_->connection()->OnSqliteError(err, this, NULL);
   return err;
 }
 
 }  // namespace sql