Mark Supplement instead of RefCountedSupplement in NavigatorContentUtils

There is no big reason that NavigatorContentUtils should use RefCountedSupplement. This CL marks the NavigatorContentUtils to use Supplement instead of RefCountedSupplement. Additionally this cl adds a tracing method for supplement.

BUG=none

Review URL: https://codereview.chromium.org/235023003

git-svn-id: svn://svn.chromium.org/blink/trunk@171403 bbb929c8-8fbe-4397-9dbb-9b2b20218538