Right-aligned text with leading/trailing spaces rendered incorrectly

Using a simple test like this:

``` js
ctx.font = '30px Arial';
ctx.textAlign = 'right';
ctx.strokeRect(100, 100, 100, 100);
ctx.fillText(' foobar', 100, 100);
```

... I'm getting incorrect rendering in latest node-canvas:


compare to the same output in Chrome (and FF):


There's a similar problem with trailing spaces.

node-canvas:


Chrome (FF):