Improve scheme validation check in NavigatorContentUtils

Though r174748 added a test case to check if scheme contains colon,
it would be better if scheme contains colon explicitly. This cl checks
scheme contains colon. if so, this cl generates syntax error exception.

BUG=none

Review URL: https://codereview.chromium.org/298273008

git-svn-id: svn://svn.chromium.org/blink/trunk@175104 bbb929c8-8fbe-4397-9dbb-9b2b20218538