style: paint-order parsing has off-by-one error.

A couple of firefox only WPT failure caused by this off-by-one bug.

Differential Revision: https://phabricator.services.mozilla.com/D35630

components/style/values/specified/svg.rs

@@ -200,7 +200,7 @@ impl Parse for SVGPaintOrder {
 
         // fill in rest
         for i in pos..PAINT_ORDER_COUNT {
-            for paint in 0..PAINT_ORDER_COUNT {
+            for paint in 1..(PAINT_ORDER_COUNT + 1) {
                 // if not seen, set bit at position, mark as seen
                 if (seen & (1 << paint)) == 0 {
                     seen |= 1 << paint;