Return ERR_INVALID_RESPONSE when we get a funky error page mime-type.

content/browser/loader/buffered_resource_handler.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 "content/browser/loader/buffered_resource_handler.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 347 matching lines @@
 
 bool BufferedResourceHandler::UseAlternateNextHandler(
     scoped_ptr<ResourceHandler> new_handler) {
   if (response_->head.headers.get() &&  // Can be NULL if FTP.
       response_->head.headers->response_code() / 100 != 2) {
     // The response code indicates that this is an error page, but we don't
     // know how to display the content.  We follow Firefox here and show our
     // own error page instead of triggering a download.
     // TODO(abarth): We should abstract the response_code test, but this kind
     //               of check is scattered throughout our codebase.
-    request()->CancelWithError(net::ERR_FILE_NOT_FOUND);
+    request()->CancelWithError(net::ERR_INVALID_RESPONSE);
     return false;
   }
 
   int request_id = GetRequestID();
 
   // Inform the original ResourceHandler that this will be handled entirely by
   // the new ResourceHandler.
   // TODO(darin): We should probably check the return values of these.
   bool defer_ignored = false;
   next_handler_->OnResponseStarted(request_id, response_.get(), &defer_ignored);
@@ skipping 98 matching lines @@
   request()->LogUnblocked();
   bool defer = false;
   if (!ProcessResponse(&defer)) {
     controller()->Cancel();
   } else if (!defer) {
     controller()->Resume();
   }
 }
 
 }  // namespace content