Revert of HttpServer: avoid DCHECK'ing on non-HTTP/1.1 requests. (https://codereview.chromium.org/251213004/)

Reason for revert:
Speculative revert since it might cause http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%282%29/builds/20802.

Original issue's description:
> HttpServer: avoid DCHECK'ing on non-HTTP/1.1 requests.
> 
> BUG=b/14249697
> R=mef@chromium.org,byungchul@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=267066

TBR=byungchul@chromium.org,mef@chromium.org,gunsch@google.com,gunsch@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=b/14249697

Review URL: https://codereview.chromium.org/265603002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@267149 0039d316-1c4b-4281-b951-d872f2087c98

• net/http/http_response_headers.cc[diff]
• net/http/http_response_headers.h[diff]
• net/http/http_util.cc[diff]
• net/http/http_util.h[diff]
• net/server/http_server.cc[diff]
• net/server/http_server_request_info.h[diff]
• net/server/http_server_unittest.cc[diff]