DevTools: [Styles] Don't set the caret to start of an active property value editor on click

R=vsevik
BUG=274811

Review URL: https://chromiumcodereview.appspot.com/24072003

git-svn-id: svn://svn.chromium.org/blink/trunk@157599 bbb929c8-8fbe-4397-9dbb-9b2b20218538