Add an optional performance bar to view performance metrics for the current page

Merged username-removed-128633 requested to merge 29010-perf-bar into master

EE MR at https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/2104:

What does this MR do?

It adds a perf bar (using https://github.com/peek/peek) that can be enabled with the p b shortcut.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots

The bar

Screen_Shot_2017-06-07_at_16.55.04

SQL queries & duration (sorted by duration DESC) shown in a modal

Screen_Shot_2017-06-07_at_16.46.32

RBlineprof modal with syntax highlighting with Rouge

Screen_Shot_2017-06-07_at_16.46.41

Shortcut documented in the shortcuts modal

Screen_Shot_2017-06-07_at_16.59.24

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Closes #29010 (closed)

Edited by username-removed-128633