Changed border default for theme_grey() (#3414, fixes #3180)

* Changed theme_grey() setting for legend key so that it creates no border (NA) rather than drawing a white one.

* update visual test cases for theme_gray() updates

Author: annennenne

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 (development version)
 
+* Changed `theme_grey()` setting for legend key so that it creates no 
+  border (`NA`) rather than drawing a white one. (@annennenne, #3180)
+
 * Added function `ggplot_add.by()` for lists created with `by()` (#2734, @Maschette)
 
 * `ggdep()` was deprecated (@perezp44, #3382).

R/theme-defaults.r

@@ -169,7 +169,7 @@ theme_grey <- function(base_size = 11, base_family = "",
     legend.spacing.x =    NULL,
     legend.spacing.y =    NULL,
     legend.margin =      margin(half_line, half_line, half_line, half_line),
-    legend.key =         element_rect(fill = "grey95", colour = "white"),
+    legend.key =         element_rect(fill = "grey95", colour = NA),
     legend.key.size =    unit(1.2, "lines"),
     legend.key.height =  NULL,
     legend.key.width =   NULL,