Wrong rendering for data-driven text-size + icon-text-fit

[jfirebaugh]

This is a specific example of #3044:

mapbox-gl-js/src/symbol/quads.js

Line 74 in 3b7187a

size = layout['text-size'] / 24,

If text-size is data-driven, this code is incorrect. What needs to happen is that the evaluated value for the current feature is passed in. Here's native implementing that:

https://github.com/mapbox/mapbox-gl-native/blob/a71756ea8d62cb448963a59e215e1324cfd57d9f/src/mbgl/text/quads.cpp#L18