Fixing pixelated artifacts around the edges of outlined text in Java 7.

This is caused by a combination of the way we draw a pixel outline and the overlapping of the edges of antialiased text in Java 7 (seems fine in Java 6). Pushing the outline drawing down into platform specific classes so that the antialiasing can be toggled for Java.
These colors help demonstrate the pixel outline antialiasing issue in
Java 7.
Text outline rendering moved from TextLayout to Canvas.