DevTools: [Console] ObjectPropertiesSection edit should not change height

This patch prettifies ObjectPropertiesSection editing so that it doesn't
change its height any more when edited.

As a side-effect, this fixes editing bug in viewported console. That is
because it doesn't trigger "scroll" event anymore as the height of the
element does not change.

BUG=385029

Review URL: https://codereview.chromium.org/375323003

git-svn-id: svn://svn.chromium.org/blink/trunk@177751 bbb929c8-8fbe-4397-9dbb-9b2b20218538