Feedback from UI review: We should use the hostname, not the full path.

I commented in an email thread, but per Enamel's URL display standards should also show the scheme unless it's guaranteed to be HTTPS.

I strongly recommend FormatUrlForSecurityDisplay() if that looks good.

karandeepb@ has joined the extensions team, and is looking for some good first bugs.

Settings Override API is only enabled on Windows(Stable) and Mac(Trunk) currently.

Also, following up from #3, I think that it's more important to be consistent with the rest of the extension prompt permissions (which omit scheme).  I'd be fine with having a discussion of moving them all over, but for now, I'd like to stay consistent.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0fdd4984f81bebc66dc2c36e4336f60328802ff9

commit 0fdd4984f81bebc66dc2c36e4336f60328802ff9
Author: karandeepb <karandeepb@chromium.org>
Date: Wed Feb 08 00:04:47 2017

Extensions: Only display host name for the overridden home and start-up pages.

Currently, the full path is shown for the home and start-up settings override
permissions. This makes the dialog UI look badly formatted and
incomprehensible. This CL changes the dialogs to only show the host name for
the overridden home and start-up pages. Existing tests are also modified.

BUG= 670890 
TEST=On Mac(trunk only) or Windows, open
https://chrome.google.com/webstore/detail/msn-homepage/ibflkkanbidceofpmolhpijgminhbmnm.
Click on Add to Chrome. Ensure only the host name is shown (without the www
prefix) for the new home and start-up page, on the dialog which shows up.

Review-Url: https://codereview.chromium.org/2676393002
Cr-Commit-Position: refs/heads/master@{#448805}

[modify] https://crrev.com/0fdd4984f81bebc66dc2c36e4336f60328802ff9/chrome/common/extensions/manifest_handlers/settings_overrides_handler.cc
[modify] https://crrev.com/0fdd4984f81bebc66dc2c36e4336f60328802ff9/chrome/common/extensions/permissions/settings_override_permission_unittest.cc