
Because you can already tab through gr-buttons, the paper-button made it
so that each button had two tabs. The tabindex should only be on the
gr-buttons, so disallow on paper-button. For easy demonstration of this
issue, try to tab through the labels on the reply dilog.
Change-Id: Ibc1e7d753f3cda1786d09f81433656c9d3282305
(cherry picked from commit 048e8dc960
)