Fix fill color alpha in layoutlib

new Color(int) ignores the upper 8 bits - it creates a color without
an alpha channel.  In order to pass in rgba we have to use a different
constructor, new Color(int,true).

(In the layout library API we should also specify that the custom
color, if specified, needs to include an alpha, or in particular add
in 0xFF<<24 if the color is opaque.)

Change-Id: I1c44caed8a5780e61b1c799f3b45bef3eb7bc97b