Clear statement before closing db in cookie code.

sql/statement.h

 // Copyright (c) 2011 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.
 
 #ifndef SQL_STATEMENT_H_
 #define SQL_STATEMENT_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 37 matching lines @@
   // you initialize it via Assign.
   Statement();
 
   explicit Statement(scoped_refptr<Connection::StatementRef> ref);
   ~Statement();
 
   // Initializes this object with the given statement, which may or may not
   // be valid. Use is_valid() to check if it's OK.
   void Assign(scoped_refptr<Connection::StatementRef> ref);
 
+  // Resets the statement to an uninitialized state corrosponding to
+  // the default constructor, releasing the StatementRef.
+  void Clear();
+
   // Returns true if the statement can be executed. All functions can still
   // be used if the statement is invalid, but they will return failure or some
   // default value. This is because the statement can become invalid in the
   // middle of executing a command if there is a serious error and the database
   // has to be reset.
   bool is_valid() const { return ref_->is_valid(); }
 
   // These operators allow conveniently checking if the statement is valid
   // or not. See the pattern above for an example.
   // TODO(shess,gbillock): Remove these once clients are converted.
@@ skipping 113 matching lines @@
 
   // See Succeeded() for what this holds.
   bool succeeded_;
 
   DISALLOW_COPY_AND_ASSIGN(Statement);
 };
 
 }  // namespace sql
 
 #endif  // SQL_STATEMENT_H_