Extensions page: fix scrollbar regression when toggling dev mode

R=dpapad@chromium.org
BUG=930042

Change-Id: Ic20ceb781e363b033a56fbd541dabecd52f2158f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1497541
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Auto-Submit: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637597}
2 files changed