Graphics and text blurry on Hi-DPI displays like Retina Macbook

[Mike McCracken]

From Zach Bir via email:
"Zeroth World Problem: I noticed in this latest build that neither the text nor the graphics are crisp on Retina displays. This is a regression. The version I downloaded on 22 August had very crisp text and the lines stroking the tabs and buttons were very crisp."

I suspect that this is related to our fix for bug 1018918 -- the version with the crisp graphics was before changing to --graphicssystem raster, and changing away from the native graphics rendering backend seems like it'd affect HiDPI rendering.