Implement shortcut for finalizing a trial with all remaining probability

It is helpful when defining experiments to put all remaining probability
on the final (often the "control" group), without having to keep a careful
tally of assignments of probabilities.  This CL implements that functionality.

r=rvargas
Review URL: http://codereview.chromium.org/150141

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@19696 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed