Revert HTTP/0.9 removal (https://codereview.chromium.org/2144803002/)

net/http/http_stream_parser.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/http/http_stream_parser.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 839 matching lines @@
     }
 
     // Parse things as well as we can and let the caller decide what to do.
     int end_offset;
     if (response_header_start_offset_ >= 0) {
       // The response looks to be a truncated set of HTTP headers.
       io_state_ = STATE_READ_BODY_COMPLETE;
       end_offset = read_buf_->offset();
       RecordHeaderParserEvent(HEADER_ALLOWED_TRUNCATED_HEADERS);
     } else {
-      // The server is apparently returning a very short HTTP/0.9 response.
-      // TODO(mmenke): Clean up remnants of HTTP/0.9 code once HTTP/0.9 removal
-      // successfully ships.
+      // The response is apparently using HTTP/0.9.  Treat the entire response
+      // as the body.
       end_offset = 0;
-      // Treat it as an error.
-      return ERR_INVALID_HTTP_RESPONSE;
     }
     int rv = ParseResponseHeaders(end_offset);
     if (rv < 0)
       return rv;
     return result;
   }
 
   if (result < 0) {
     io_state_ = STATE_DONE;
     return result;
@@ skipping 77 matching lines @@
   }
 
   if (response_header_start_offset_ >= 0) {
     end_offset = HttpUtil::LocateEndOfHeaders(read_buf_->StartOfBuffer(),
                                               read_buf_->offset(),
                                               response_header_start_offset_);
   } else if (read_buf_->offset() >= 8) {
     // Enough data to decide that this is an HTTP/0.9 response.
     // 8 bytes = (4 bytes of junk) + "http".length()
     end_offset = 0;
-    // Treat a an error.
-    return ERR_INVALID_HTTP_RESPONSE;
   }
 
   if (end_offset == -1)
     return -1;
 
   int rv = ParseResponseHeaders(end_offset);
   if (rv < 0)
     return rv;
   return end_offset;
 }
@@ skipping 247 matching lines @@
   UMA_HISTOGRAM_ENUMERATION("Net.HttpStatusLineStatus", status,
                             HttpStatusLineValidator::STATUS_LINE_MAX);
 }
 
 bool HttpStreamParser::SendRequestBuffersEmpty() {
   return request_headers_ == nullptr && request_body_send_buf_ == nullptr &&
          request_body_send_buf_ == nullptr;
 }
 
 }  // namespace net