In change metadata, add a "Votable: " section to the tooltip that
contains detailed info on labels that reviewer can grant. If reviewer
can't grant labels, "Votable" part is not included in tooltip.
Show label with maximal permitted score if reviewer is allowed to give
it. If the reviewer is not allowed for maximal score, show label only.
Examples:
Reviewer can grant Code-Review+2. Tooltip in this case will contain
"Votable: Code-Review +2"
Reviewer can grant Code-Review+1, while +2 is the maximum
permitted. Tooltip in this case will contain "Votable: Code-Review"
GWT implementation in Change 87970
Feature: Issue 4528
Change-Id: I1842d519ea013f07b190c9f6c48f0690b7670a06
8de21ebfed