8024261: xrender: improve performance of small fillRect operations

Reviewed-by: prr, bae

src/solaris/classes/sun/java2d/xr/XRCompositeManager.java

@@ -285,7 +285,12 @@ public class XRCompositeManager {
         if (xorEnabled) {
             con.GCRectangles(dst.getXid(), dst.getGC(), rects);
         } else {
-            con.renderRectangles(dst.getPicture(), compRule, solidColor, rects);
+            if (rects.getSize() == 1) {
+                con.renderRectangle(dst.getPicture(), compRule, solidColor,
+                        rects.getX(0), rects.getY(0), rects.getWidth(0), rects.getHeight(0));
+            } else {
+                con.renderRectangles(dst.getPicture(), compRule, solidColor, rects);
+            }
         }
     }