API Review: Paint#isOpaque

[Richard Bair]

Hi all,

As part of the region fixes I'm doing, I've added an "isOpaque" flag to Paint and implemented it in Color, LinearGradient, and RadialGradient. The implementation in ImagePattern is a no-op (just returns false) pending a fix for http://javafx-jira.kenai.com/browse/RT-24827. I basically took functionality in Prism's Paint and duplicated on the public API level so as to give me the ability to determine the opaque insets on the Region level (saving per-render computation overhead).

Thanks
Richard