[DevTools] Make network summary bar text selectable

I know this is not the best solution to this problem, so I made another
bug where we can explore a better option: http://crbug.com/964493

Bug: 962926
Change-Id: Ib7ff0d196b5eb0fbbc70feeaf28aad188d3e6ebc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1618168
Reviewed-by: Erik Luo <luoe@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661470}
1 file changed