Need to check invalid scheme in navigator content utils

According to spec, scheme value should not contain a colon. So, this cl checks if scheme contains a colon.

"The scheme value, if it contains a colon (as in "mailto:"), will never match anything, since schemes don't contain colons."

Spec: http://www.whatwg.org/specs/web-apps/current-work/#custom-handlers

BUG=none

Review URL: https://codereview.chromium.org/292203007

git-svn-id: svn://svn.chromium.org/blink/trunk@174748 bbb929c8-8fbe-4397-9dbb-9b2b20218538