DevTools: Remove 1px of dead space between elements tree items
DevTools: Remove 1px of dead space between elements tree items

There was 1px of margin on items in the elements tree outline. If that
area was clicked, selecting a new element would fail.

Change-Id: I62c3aeb814759349c05582ac6b23309901e6d98e
Reviewed-on: https://chromium-review.googlesource.com/c/1387453
Reviewed-by: Pavel Feldman <e1161d7019a0d5c7981e3c3ffc69c76f4b09679a@chromium.org>
Commit-Queue: Joel Einbinder <bab755abe9fee48fe544272e55f73517d4e4a725@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#628193}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 12e6395ca993404b881e17c0e7540dd0bd197e75
ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend