Google Chrome	61.0.3135.4 (Official Build) dev (64-bit)
Revision	8366065c0da06984379f2d39bc85c1067d70d3dd-refs/branch-heads/3135@{#8}
OS	Linux
JavaScript	V8 6.1.191

What steps will reproduce the problem?
(1) Got to the page  https://dart-review.googlesource.com/#/c/2241/
(2) Click on the link https://chromium.googlesource.com/chromium/src/+/infra/config/cr-buildbucket.cfg in comment 3.
(3) A new page opens with the URL set to https://chromium.googlesource.com/chromium/src/%20/infra/config/cr-buildbucket.cfg#   . This page does not exist, so returns a 404
(4) Go back to the page with the link, and click a second time.
(5) A new page opens with the correct URL, https://chromium.googlesource.com/chromium/src/+/infra/config/cr-buildbucket.cfg

What is the expected result?
That the link opens with the target URL unchanged, as it does the second time you click.

This has been happening on multiple pages, all git browsing URLs with a + in them, where it is rewritten to %20 the first time the link is followed.

Opening the same page in a new tab, and repeating the steps, does not reproduce the problem.

Creating a new comment with a similar URL did not reproduce the problem.