RDH: Don't attempt to sniff the mime type of requests that...

chrome/browser/renderer_host/buffered_resource_handler.cc

 // Copyright (c) 2006-2008 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 "chrome/browser/renderer_host/buffered_resource_handler.h"
 
 #include "base/histogram.h"
 #include "base/logging.h"
 #include "base/string_util.h"
 #include "net/base/mime_sniffer.h"
@@ skipping 133 matching lines @@
 bool BufferedResourceHandler::DelayResponse() {
   std::string mime_type;
   request_->GetMimeType(&mime_type);
 
   std::string content_type_options;
   request_->GetResponseHeaderByName("x-content-type-options",
                                     &content_type_options);
 
   const bool sniffing_blocked =
       LowerCaseEqualsASCII(content_type_options, "nosniff");
+  const bool no_data =
+      response_->response_head.headers &&  // Can be NULL if FTP.
+      (response_->response_head.headers->response_code() == 304 ||

[eroman, 2009/09/01 03:30:58]

I'm not sure that it is appropriate to put HTTP-code specific stuff outside of
the net/http module (I know we do this in other places, but that seems wrong).

In particular, this seems like logic duplicated from
http_network_transaction.cc.

Moreover, I don't think this list is exhaustive. For example, HEAD requests can
never have a body, regardless of the HTTP status code.

See HttpNetworkTransaction::DidReadResponseHeaders() which tries to handle all
of these cases in setting up |response_body_length_|.

I think it would be better to unify these interpretations of HTTP codes --
either by using shared functions living in src/net/http, or by exporting the
information from the network module through some field in the response object.

(Sorry to pitch in late, only just got back from vacation).

+       response_->response_head.headers->response_code() == 204);
   const bool we_would_like_to_sniff =
-      net::ShouldSniffMimeType(request_->url(), mime_type);
+      no_data ? false : net::ShouldSniffMimeType(request_->url(), mime_type);
 
   RecordSnifferMetrics(sniffing_blocked, we_would_like_to_sniff, mime_type);
 
   if (!sniffing_blocked && we_would_like_to_sniff) {
     // We're going to look at the data before deciding what the content type
     // is.  That means we need to delay sending the ResponseStarted message
     // over the IPC channel.
     sniff_content_ = true;
     LOG(INFO) << "To buffer: " << request_->url().spec();
     return true;
   }
 
-  if (sniffing_blocked && mime_type.empty()) {
+  if (sniffing_blocked && mime_type.empty() && !no_data) {
     // Ugg.  The server told us not to sniff the content but didn't give us a
     // mime type.  What's a browser to do?  Turns out, we're supposed to treat
     // the response as "text/plain".  This is the most secure option.
     mime_type.assign("text/plain");
     response_->response_head.mime_type.assign(mime_type);
   }
 
   if (ShouldBuffer(request_->url(), mime_type)) {
     // This is a temporary fix for the fact that webkit expects to have
     // enough data to decode the doctype in order to select the rendering
     // mode.
     should_buffer_ = true;
     LOG(INFO) << "To buffer: " << request_->url().spec();
     return true;
   }
 
-  if (ShouldWaitForPlugins()) {
+  if (!no_data && ShouldWaitForPlugins()) {
     wait_for_plugins_ = true;
     return true;
   }
 
   return false;
 }
 
 bool BufferedResourceHandler::ShouldBuffer(const GURL& url,
                                            const std::string& mime_type) {
   // We are willing to buffer for HTTP and HTTPS.
@@ skipping 232 matching lines @@
   wait_for_plugins_ = false;
   if (request_) {
     ResourceDispatcherHost::ExtraRequestInfo* info =
         ResourceDispatcherHost::ExtraInfoForRequest(request_);
     host_->PauseRequest(info->process_id, info->request_id, false);
     if (!CompleteResponseStarted(info->request_id, false))
       host_->CancelRequest(info->process_id, info->request_id, false);
   }
   Release();
 }