[sql] Complain about statement mutations after stepping has started.

sql/statement.h

 // 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.
 
 #ifndef SQL_STATEMENT_H_
 #define SQL_STATEMENT_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 160 matching lines @@
   // situations may. Therefore, the code is handling disjoint situations in
   // release and test. In test, we're ensuring correct SQL. In release, we're
   // ensuring that contracts are honored in error edge cases.
   bool CheckValid() const;
 
   // The actual sqlite statement. This may be unique to us, or it may be cached
   // by the connection, which is why it's refcounted. This pointer is
   // guaranteed non-NULL.
   scoped_refptr<Connection::StatementRef> ref_;
 
+  // Set after Step() or Run() are called, reset by Reset().  Used to
+  // prevent accidental calls to API functions which would not work
+  // correctly after stepping has started.
+  bool stepped_;
+
   // See Succeeded() for what this holds.
   bool succeeded_;
 
   DISALLOW_COPY_AND_ASSIGN(Statement);
 };
 
 }  // namespace sql
 
 #endif  // SQL_STATEMENT_H_