Fix rounding error in Palette's region calculation

Can result in Bitmap.getPixels() throwing a
IllegalArgumentException with certain bitmaps.

I've haven't been able to recreate the issue but it's
guaranteed not to happen now with this CL.

BUG: 25760671

Change-Id: I12648bb59d2c281a5cd0c2c7e3dcf0fe7df3e200
1 file changed