DevTools: IndexDB view: fix alignment and simplify CSS.

Screenshots:

Before:
http://picpaste.com/before.png

After:
http://picpaste.com/after.png

BUG=

Review URL: https://codereview.chromium.org/510513004

git-svn-id: svn://svn.chromium.org/blink/trunk@180949 bbb929c8-8fbe-4397-9dbb-9b2b20218538