This makes the metrics tab "bars" clickable.

  Clicking on any of the bars displays a list of students for that
  particular action (either opened the subsection or attempted the
  problem).
  Students are listed for the sub-sections.
  Students, grade and percent are listed for the problems.
  The on-screen list displays only the first 250 students with
  an overflow message if there are more students than that.
  The csv download lists all students.
Merge pull request #3240 from edx/dcadams/enhanced_metric_reporting

This makes the metrics tab "bars" clickable.