GitLab

This includes the following changes:
- Material design icons to match the current mocks better.
- Rename securityPanel.css into mainView.css, because it only contains main view CSS anyhow.
- Rewrite security panel main view DOM code to match the mocks.

BUG=484387

Review URL: https://codereview.chromium.org/1316853002

git-svn-id: svn://svn.chromium.org/blink/trunk@201267 bbb929c8-8fbe-4397-9dbb-9b2b20218538