panel.grid.major incorrectly translated

Likely introduced by https://github.com/tidyverse/ggplot2/commit/caca650c2a7891fdc7d7f14c377845bce46673f4

```r
ggplotly(qplot(1:10))
```

![screen shot 2018-01-24 at 3 00 32 pm](https://user-images.githubusercontent.com/1365941/35356879-5b5716a8-0117-11e8-9e7b-984476b063e3.png)
