Remove chrome-internal scheme, chrome::kChromeInternalScheme.

The chrome-internal scheme was once used to host the NTP.
It's now hosted at about:newtab, aka. chrome://newtab.
There's no compelling reason to support chrome-internal.

BUG=6564,327845
R=jam@chromium.org
TEST=chrome-internal://foo no longer redirects to the new tab page, no one gets upset.

Review URL: https://codereview.chromium.org/114883002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240819 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240819