The following SVG element should render as a lozenge/capsule with two rounded ends. Instead, the 180 degree turn causes the right edge to be drawn flat.
<polyline points="0,0 10,0 -10,0" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="70" />
Changing one of the y coordinates to non-zero (e.g. 0.1) results in the correct display.
This bug is present in Safari v5.0.4 and the latest nightly Webkit.
Created attachment 87554 [details]
Simple test case with the reported problematic markup.
I don't see the problem on WebKit for Mac. Should it be platform specific (WebKitGtk/EFL), please reopen the bug and prefix the title with [Cairo].