Implement sql::Connection::Raze() in terms of sqlite3_backup API.

sql/connection.h

Index: sql/connection.h
diff --git a/sql/connection.h b/sql/connection.h
index 9b81804bc1fafb68bac8bfb9a63dff4c6887305c..1e3414f40ca72912b0b8e0b64af1fa37d5e78a1f 100644
--- a/sql/connection.h
+++ b/sql/connection.h
@@ -181,6 +181,26 @@ class SQL_EXPORT Connection {
   // generally exist either.
   void Preload();
 
+  // Raze the database to the ground.  This approximates creating a
+  // fresh database from scratch, within the constraints of SQLite's
+  // locking protocol (locks and open handles can make doing this with
+  // filesystem operations problematic).  Returns true if the database
+  // was razed.
+  //
+  // false is returned if the database is locked by some other
+  // process.  RazeWithTimeout() may be used if appropriate.
+  //
+  // NOTE(shess): Raze() will DCHECK in the following situations:
+  // - database is not open.
+  // - the connection has a transaction open.
+  // - a SQLite issue occurs which is structural in nature (like the
+  //   statements used are broken).
+  // Since Raze() is expected to be called in unexpected situations,
+  // these all return false, since it is unlikely that the caller
+  // could fix them.
+  bool Raze();
+  bool RazeWithTimout(base::TimeDelta timeout);
+
   // Transactions --------------------------------------------------------------
 
   // Transaction management. We maintain a virtual transaction stack to emulate