Fixing up some APIs to allow Web DB to work from dart and adding tests.

tests/html/websql_test.dart

+#library('WebDBTest');
+#import('../../pkg/unittest/unittest.dart');
+#import('../../pkg/unittest/html_config.dart');
+#import('dart:html');
+
+void fail(message) {
+  guardAsync(() {
+      Expect.fail(message);
+    });
+}
+
+Future<SQLTransaction> createTransaction(Database db) {
+  final completer = new Completer<SQLTransaction>();
+
+  db.transaction((SQLTransaction transaction) {
+    completer.complete(transaction);
+  });
+
+  return completer.future;
+}
+
+createTable(tableName, columnName) => (SQLTransaction transaction) {
+  final completer = new Completer<SQLTransaction>();
+
+  final sql = 'CREATE TABLE $tableName ($columnName)';
+  transaction.executeSql(sql, [],
+    (SQLTransaction tx, SQLResultSet rs) {
+      completer.complete(transaction);
+    },
+    (SQLTransaction tx, SQLError error) {
+      fail(error.message);
+    });
+
+  return completer.future;
+};
+
+insert(tableName, columnName, value) => (SQLTransaction transaction) {
+  final completer = new Completer<SQLTransaction>();
+
+  final sql = 'INSERT INTO $tableName ($columnName) VALUES (?)';
+  transaction.executeSql(sql, [value],
+    (SQLTransaction tx, SQLResultSet rs) {
+      completer.complete(tx);
+    },
+    (SQLTransaction tx, SQLError error) {
+      fail(error.message);
+    });
+
+  return completer.future;
+};
+
+queryTable(tableName, callback) => (SQLTransaction transaction) {
+  final completer = new Completer<SQLTransaction>();
+
+  final sql = 'SELECT * FROM $tableName';
+  transaction.executeSql(sql, [],
+    (SQLTransaction tx, SQLResultSet rs) {
+      callback(rs);
+      completer.complete(tx);
+    },
+    (SQLTransaction tx, SQLError error) {
+      fail(error.message);
+    });
+
+  return completer.future;
+};
+
+dropTable(tableName, [bool ignoreFailure = false]) =>
+    (SQLTransaction transaction) {
+  final completer = new Completer<SQLTransaction>();
+
+  final sql = 'DROP TABLE $tableName';
+  transaction.executeSql(sql, [],
+    (SQLTransaction tx, SQLResultSet rs) {
+      completer.complete(tx);
+    },
+    (SQLTransaction tx, SQLError error) {
+      if (ignoreFailure) {
+        completer.complete(tx);
+      } else {
+        fail(error.message);
+      }
+    });
+
+  return completer.future;
+};
+
+main() {
+  useHtmlConfiguration();
+
+  test('Web Database', () {
+    final tableName = 'test_table';
+    final columnName = 'test_data';
+
+    final db = window.openDatabase('test_db', '1.0', 'test_db', 1024 * 1024);
+
+    Expect.isNotNull(db, 'Unable to open database');
+
+    createTransaction(db)
+      // Attempt to clear out any tables which may be lurking from previous
+      // runs.
+      .chain(dropTable(tableName, true))
+      .chain(createTable(tableName, columnName))
+      .chain(insert(tableName, columnName, 'Some text data'))
+      .chain(queryTable(tableName, (resultSet) {
+        guardAsync(() {
+          Expect.equals(1, resultSet.rows.length);
+
+          // Should validate the rowData contents- need to be able to map the JS
+          // object back to regular types.
+        });
+      }))
+      .chain(dropTable(tableName))
+      .then(expectAsync1((tx) {}));
+  });
+}