[Default App]Set the default app of Web Browser to Chromium. Double click the html file. It's still opened by Foxfire.

[Machine]
Dell Vostro 3900
  [Version]
18.04 daily 20180412 +
kylin-video_1.1.6-0ubuntu2、
youker-assistant_3.0.4、
Ukui-control-center_1.1.2-0ubuntu1

  [Details]
[Default App]Set the default app of Web Browser to Chromium. Double click the html file. It's still opened by Foxfire.
【网络浏览器】将默认应用更改为chromium，双击桌面上的html文件，仍旧是Firefox打开的

  [Test Case]
1. Open the start menu - Settings-Default App
2. Set the default app of Web Browser to Chromium
3. Double click the html file.
Expected Result:Opened by Chromium
Actual Result:It's still opened by Foxfire.