Change Lite Page Previews Host DCHECK

This DCHECK is especially annoying when testing on localhost when the
server is not HTTPS. This changes the DCHECK to be a lot simpler. Open
to other ideas to the same effect but the only alternative seems to be
DCHECKing the finch param which doesn't seem better or worse.

Bug: 864635
Change-Id: Icf7b12991acd2c6bab2cd13c4a40ff4bef1dcee1
Reviewed-on: https://chromium-review.googlesource.com/1227353Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591511}

chrome/browser/previews/previews_lite_page_navigation_throttle.cc

@@ -201,7 +201,7 @@ GURL PreviewsLitePageNavigationThrottle::GetPreviewsURLForURL(
       (previews_host.has_port() ? (":" + previews_host.port()) : "") + "/p?u=" +
       net::EscapeQueryParamValue(original_url.spec(), true /* use_plus */));
   DCHECK(previews_url.is_valid());
-  DCHECK(previews_url.SchemeIs(url::kHttpsScheme));
+  DCHECK_EQ(previews_host.scheme(), previews_url.scheme());
   return previews_url;
 }