I noticed that over the last day or two the outlines are no longer drawn if the line style is "dashed". Solid outlines draw correctly.
Created attachment 11946 [details] test case showing dashed outline not drawn.
If I change the outline width to 2px or higher it is drawn. Borders are affected in the same way. Those max(strokeThickness, 1.0f) in GraphicsContextCG were doing something after all :-)
Created attachment 11949 [details] Patch
*** Bug 11918 has been marked as a duplicate of this bug. ***
Comment on attachment 11949 [details] Patch r=me
Committed revision 18392.