Add diamond test code
Render border solid-style properly
auto merge of #1322 : jdm/servo/renderborder, r=jdm

Implemented a border which was the solid type.
Because of not support css pseudo element(:before, :after), content in css property and base64, So we couldn't test Acid2(http://www.webstandards.org/files/acid2/test.html).

Rebase of #1276.