Fix short error responses sniffed as downloads hanging.

content/browser/loader/mime_sniffing_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/mime_sniffing_resource_handler.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 527 matching lines @@
   }
 
   // Attempt to intercept the request as a stream.
   base::FilePath plugin_path;
   if (has_plugin)
     plugin_path = plugin.path;
   std::string payload;
   std::unique_ptr<ResourceHandler> handler(host_->MaybeInterceptAsStream(
       plugin_path, request(), response_.get(), &payload));
   if (handler) {
-    if (!CheckResponseIsNotProvisional()) {
-      Cancel();
+    if (!CheckResponseIsNotProvisional())
       return false;
-    }
     *handled_by_plugin = true;
     intercepting_handler_->UseNewHandler(std::move(handler), payload);
   }
 #endif
   return true;
 }
 
 bool MimeSniffingResourceHandler::CanBeIntercepted() {
   if (response_->head.headers.get() &&
       response_->head.headers->response_code() == 304) {
     return false;
   }
 
   return true;
 }
 
 bool MimeSniffingResourceHandler::CheckResponseIsNotProvisional() {
   if (!response_->head.headers.get() ||
       response_->head.headers->response_code() / 100 == 2) {
     return true;
   }
 
   // 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 intercepting the request as a stream or 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_INVALID_RESPONSE);
+  CancelWithError(net::ERR_INVALID_RESPONSE);

[mmenke, 2017/07/06 17:51:56]

I verified that we should be holding onto a controller at both the places this
is called from.

   return false;
 }
 
 bool MimeSniffingResourceHandler::MustDownload() {
   if (must_download_is_set_)
     return must_download_;
 
   must_download_is_set_ = true;
 
   std::string disposition;
@@ skipping 14 matching lines @@
 
 void MimeSniffingResourceHandler::OnPluginsLoaded(
     const std::vector<WebPluginInfo>& plugins) {
   // No longer blocking on the plugins being loaded.
   request()->LogUnblocked();
   if (state_ == STATE_BUFFERING)
     AdvanceState();
 }
 
 }  // namespace content