DevTools: Breakpoints should be blurred when breakpoints are deactivated.

BUG=296771
R=lushnikov, pfeldman

Review URL: https://chromiumcodereview.appspot.com/24197004

git-svn-id: svn://svn.chromium.org/blink/trunk@158260 bbb929c8-8fbe-4397-9dbb-9b2b20218538