[dom] Fix DOM XY tests stuff

This change fixes some stuff on DOM XY tests as follows.

1. Both the expected and actual values should be normalized by `Math.floor()` or `Math.ceil()` functions because the expected values on [Chrome 36][chrome36] (currently Beta) returns fractional values, the actual values on Firefox 29 (Stable) returns fractional values.
2. The `testXY()` function's parameters is opposite. Fix the order of the parameters to avoid the confusion.
3. Clean up some unused variables.

So here is testing results on each browsers.

```
[okuryu.local](yui3@fix-dom-xy-test)$ yeti src/dom/tests/unit/dom-xy.html
  Agent connected: Firefox (29.0) / Mac OS from 127.0.0.1
  Agent connected: Chrome (36.0.1985.32) / Mac OS from 127.0.0.1
  Agent connected: Safari (7.0.4) / Mac OS from 127.0.0.1
  Agent connected: Internet Explorer (6.0) / Windows XP from 10.0.1.15
  Agent connected: Internet Explorer (7.0) / Windows XP from 10.0.1.15
  Agent connected: Internet Explorer (8.0) / Windows XP from 10.0.1.15
  Agent connected: Internet Explorer (9.0) / Windows 7 from 10.0.1.15
  Agent connected: Internet Explorer (10.0) / Windows 7 from 10.0.1.15
  Agent connected: Internet Explorer (11.0) / Windows 7 from 10.0.1.15
  Agent connected: Safari (7.0) / iOS 7.1.1 from 10.0.1.16
✓ Testing started on Firefox (29.0) / Mac OS, Chrome (36.0.1985.32) / Mac OS, Safari (7.0.4) / Mac OS, Internet Explorer (6.0) / Windows XP, Internet Explorer (7.0) / Windows XP, Internet Explorer (8.0) / Windows XP, Internet Explorer (9.0) / Windows 7, Internet Explorer (10.0) / Windows 7, Internet Explorer (11.0) / Windows 7, Safari (7.0) / iOS 7.1.1
✓ Agent completed: Safari (7.0.4) / Mac OS
✓ Agent completed: Firefox (29.0) / Mac OS
✓ Agent completed: Internet Explorer (10.0) / Windows 7
✓ Agent completed: Safari (7.0) / iOS 7.1.1
✓ Agent completed: Internet Explorer (11.0) / Windows 7
✓ Agent completed: Internet Explorer (9.0) / Windows 7
✓ Agent completed: Internet Explorer (8.0) / Windows XP
✓ Agent completed: Chrome (36.0.1985.32) / Mac OS
✓ Agent completed: Internet Explorer (6.0) / Windows XP
✓ Agent completed: Internet Explorer (7.0) / Windows XP
✓ 420 tests passed! (7 seconds)
```

[chrome36]: http://blog.chromium.org/2014/05/chrome-36-beta-elementanimate-html.html