[sql] Refactor to remove use of const_cast<>.

sql/connection.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_CONNECTION_H_
 #define SQL_CONNECTION_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 321 matching lines @@
   // A statement ref can be valid, in which case it can be used, or invalid to
   // indicate that the statement hasn't been created yet, has an error, or has
   // been destroyed.
   //
   // The Connection may revoke a StatementRef in some error cases, so callers
   // should always check validity before using.
   class SQL_EXPORT StatementRef : public base::RefCounted<StatementRef> {
    public:
     // Default constructor initializes to an invalid statement.
     StatementRef();
+    explicit StatementRef(sqlite3_stmt* stmt);
     StatementRef(Connection* connection, sqlite3_stmt* stmt);
 
     // When true, the statement can be used.
     bool is_valid() const { return !!stmt_; }
 
     // If we've not been linked to a connection, this will be NULL. Guaranteed
     // non-NULL when is_valid().
     Connection* connection() const { return connection_; }
 
     // Returns the sqlite statement if any. If the statement is not active,
@@ skipping 29 matching lines @@
   void ClearCache();
 
   // Called by Statement objects when an sqlite function returns an error.
   // The return value is the error code reflected back to client code.
   int OnSqliteError(int err, Statement* stmt);
 
   // Like |Execute()|, but retries if the database is locked.
   bool ExecuteWithTimeout(const char* sql, base::TimeDelta ms_timeout)
       WARN_UNUSED_RESULT;
 
+  // Internal helper for const functions.  Like GetUniqueStatement(),
+  // except the statement is not entered into open_statements_,
+  // allowing this function to be const.  Open statements can block
+  // closing the database, so only use in cases where the last ref is
+  // released before close could be called (which should always be the
+  // case for const functions).
+  scoped_refptr<StatementRef> GetUntrackedStatement(const char* sql) const;
+
   // The actual sqlite database. Will be NULL before Init has been called or if
   // Init resulted in an error.
   sqlite3* db_;
 
   // Parameters we'll configure in sqlite before doing anything else. Zero means
   // use the default value.
   int page_size_;
   int cache_size_;
   bool exclusive_locking_;
 
@@ skipping 20 matching lines @@
   // This object handles errors resulting from all forms of executing sqlite
   // commands or statements. It can be null which means default handling.
   scoped_refptr<ErrorDelegate> error_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(Connection);
 };
 
 }  // namespace sql
 
 #endif  // SQL_CONNECTION_H_