[sql] Log tag with sqlite errors.

sql/connection.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_CONNECTION_H_
 #define SQL_CONNECTION_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 493 matching lines @@
 
   // Executes a rollback statement, ignoring all transaction state. Used
   // internally in the transaction management code.
   void DoRollback();
 
   // Called by a StatementRef when it's being created or destroyed. See
   // open_statements_ below.
   void StatementRefCreated(StatementRef* ref);
   void StatementRefDeleted(StatementRef* ref);
 
-  // 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);
+  // Called when a sqlite function returns an error, which is passed
+  // as |err|.  The return value is the error code to be reflected
+  // back to client code.  |stmt| is non-NULL if the error relates to
+  // an sql::Statement instance.  |sql| is non-NULL if the error
+  // relates to non-statement sql code (Execute, for instance).  Both
+  // can be NULL, but both should never be set.
+  // NOTE(shess): Originally, the return value was intended to allow
+  // error handlers to transparently convert errors into success.
+  // Unfortunately, transactions are not generally restartable, so
+  // this did not work out.
+  int OnSqliteError(int err, Statement* stmt, const char* sql);
 
   // 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
@@ skipping 45 matching lines @@
 
   // Tag for auxiliary histograms.
   std::string histogram_tag_;
 
   DISALLOW_COPY_AND_ASSIGN(Connection);
 };
 
 }  // namespace sql
 
 #endif  // SQL_CONNECTION_H_