Subplot with faceted ggplots: misplaced facet strips with nrows>1

When passing faceted ggplots to subplot(), the result is rendered properly as long as nrows=1. However, once I pass nrows=2 or greater, the facet strips become misplaced.

require(ggplot)
require(plotly)

ggiris <- qplot(Petal.Width, Sepal.Length, data = iris, color = Species)
# With nrows = 1, facets are rendered properly
subplot (ggiris , ggiris+facet_wrap(~Species))
# With nrows>1, facets are messed up
subplot (ggiris , ggiris+facet_wrap(~Species), nrows=2)

This used to work correctly on my system, using a previous version of the library - I found the error after updating plotly and a bunch of other libraries. Unfortunately, I haven't been able to restore the previous environment, so I don't know on which release it stopped working.

Start by reproducing the examples in the issue with subplot(), facet_wrap(), and nrows=2, then trace the subplot entry point and its handling of faceted ggplots and row layout. Done means facet strips remain correctly positioned when nrows is greater than 1, with a regression test covering the reported example.