Remove obsolete http_base package

dart/pkg/http_base/test/http_base_html_test.dart

-library http_base.http_base_html_test;
-
-import 'dart:html';
-import 'dart:async';
-import 'dart:convert';
-
-import 'package:http_base/http_base_html.dart';
-import 'package:unittest/unittest.dart';
-
-main() {
-  test('http-client', () {
-    var uri = Uri.parse(window.location.href).resolve('/echo');
-
-    var client = new Client();
-    var body = (new StreamController()
-        ..add(UTF8.encode('my-data'))
-        ..close()).stream;
-    var request = new RequestImpl('POST', uri, body: body);
-    client(request).then(expectAsync((response) {
-      expect(response.statusCode, equals(200));
-      response.read()
-          .transform(UTF8.decoder).join('').then(expectAsync((data) {
-        expect(data, equals('my-data'));
-      }));
-    }));
-  });
-}