Steps to reproduce:

1. open perfherder page, comparing 2 revisions with multiple runs
   • https://treeherder.mozilla.org/perfherder/compare?originalProject=try&originalRevision=a9d0ae42ce3ae907c83936a8837caf06908bac81&newProject=try&newRevision=846d8787a88518999298cee6ca0b73ba8f34bc5f&framework=13&page=2&showOnlyComparable=1
2. hover over the average score for before/after

Actual result:

the graph with runs for before/after are shown separately
("Current" in the attachment)

Expected result:

The graph with runs for before/after are shown at the same time, (Proposal (A) in the attachment),
so that it's easier to compare the result with bi-modal/multi-modal behavior.

Optionally show a histogram (Proposal (B) in the attachment),
so that it's easier to see the peak shift visually.

example graph using actual data, in https://bug531915.bmoattachments.org/attachment.cgi?id=9234186

Thanks arai for the detailed suggestion. This is a really helpful enhancement for the Compare View. We'll add this task to the next grooming and planning sessions for the perfteam

Jira ticket: https://mozilla-hub.atlassian.net/browse/FXP-1698

another example that shows the graph in the table, instead of balloon