The current code assumes the the bottom left and bottom right border radius arcs start at the same Y coordinate. When the bottom left and bottom right radii are different, this is not the case. This is one of two outstanding -webkit-border-bottom-right-radius rendering bugs the other is bug 11113.
Created attachment 11501 [details] Testcase Testcase showing incorrect drawing of bottom right corner when the bottom left is a different radius. Looking at the source code, this is also a problem when rendering the right hand side but bug 11113 shows itself and I can't test it. (second box in the test case)
Created attachment 11502 [details] First look patch (no tests yet) No layout tests or ChangeLog added yet, just putting this patch up first. Simple patch, that adds calculation of the respective X and Y coordinates for the arcs in both the "drawBottom" and "drawRight" cases.
Comment on attachment 11502 [details] First look patch (no tests yet) The small change in the above patch also seems to fix http://bugs.webkit.org/show_bug.cgi?id=11113. What tests need to be written for this?
Comment on attachment 11502 [details] First look patch (no tests yet) Looks good! Your test should a box whose bottom-left, bottom-right and top-right are distinct. In order to test the second change, the bottom border and the right border should not match (e.g. have different color). You can use LayoutTests/fast/borders/borderRadiusSolid01.html as a starting point. After you make the test, you need to generate expected results. The run-webkit-tests script does that by default for tests that don't have expected results, so you just need to run it on your test. Make sure to use the --pixel option in order to have pixel results generated. Once you have the test and the expected results in your tree, use "svn add" to add them to your working copy, then use the prepare-ChangeLog script to add ChangeLog entries (one in WebCore/ChangeLog and another one in LayoutTest/ChangeLog). Edit the ChangeLogs and generate a new patch.
Created attachment 11577 [details] Patch with Layout Test and Expected results +pixel results Added a Layout Test with expected results and pixel test results
Comment on attachment 11577 [details] Patch with Layout Test and Expected results +pixel results r=me
Landed in r17869. Alex, just a note: your layout test was indented using tabs rather than spaces. Can you be sure to use spaces in future?
*** Bug 11113 has been marked as a duplicate of this bug. ***
Cool, nice to see this one fixed!