DevTools: NetworkPanel: remove unused CSS.

BUG=316092
NOTRY=true

Review URL: https://codereview.chromium.org/461383002

git-svn-id: svn://svn.chromium.org/blink/trunk@180144 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: NetworkPanel: remove noop CSS.

BUG=316092
NOTRY=true

Review URL: https://codereview.chromium.org/464813002

git-svn-id: svn://svn.chromium.org/blink/trunk@180145 bbb929c8-8fbe-4397-9dbb-9b2b20218538