Fix nextRangeU(0, MAX_UINT) div by zero.

R=reed@google.com
Review URL: https://codereview.appspot.com/7201058

git-svn-id: http://skia.googlecode.com/svn/trunk@7400 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed