Move MimeTypeResourceHandler before ThrottlingResourceHandler

content/browser/loader/resource_dispatcher_host_impl.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.
 
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
 
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 
 #include <stddef.h>
 
@@ skipping 37 matching lines @@
 #include "content/browser/loader/async_resource_handler.h"
 #include "content/browser/loader/async_revalidation_manager.h"
 #include "content/browser/loader/cross_site_resource_handler.h"
 #include "content/browser/loader/detachable_resource_handler.h"
 #include "content/browser/loader/mime_type_resource_handler.h"
 #include "content/browser/loader/navigation_resource_handler.h"
 #include "content/browser/loader/navigation_resource_throttle.h"
 #include "content/browser/loader/navigation_url_loader_impl_core.h"
 #include "content/browser/loader/power_save_block_resource_throttle.h"
 #include "content/browser/loader/redirect_to_file_resource_handler.h"
+#include "content/browser/loader/replacing_resource_handler.h"
 #include "content/browser/loader/resource_message_filter.h"
 #include "content/browser/loader/resource_request_info_impl.h"
 #include "content/browser/loader/stream_resource_handler.h"
 #include "content/browser/loader/sync_resource_handler.h"
 #include "content/browser/loader/throttling_resource_handler.h"
 #include "content/browser/loader/upload_data_stream_builder.h"
 #include "content/browser/renderer_host/render_view_host_delegate.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/resource_context_impl.h"
 #include "content/browser/service_worker/foreign_fetch_request_handler.h"
@@ skipping 1650 matching lines @@
   if (IsBrowserSideNavigationEnabled() && IsResourceTypeFrame(resource_type) &&
       child_id != -1) {
     DCHECK(request->url().SchemeIs(url::kBlobScheme));
     return handler;
   }
 
   PluginService* plugin_service = nullptr;
 #if defined(ENABLE_PLUGINS)
   plugin_service = PluginService::GetInstance();
 #endif
-  // Insert a buffered event handler before the actual one.
-  handler.reset(new MimeTypeResourceHandler(std::move(handler), this,
-                                            plugin_service, request));
+
+  // The ReplacingResourceThrottle will replace its next handler with an
+  // appropriate one based on the MIME type of the response if needed.

[mmenke, 2016/06/09 18:18:42]

Maybe mention that this must be at the end of the chain, just before |handler|?

[clamy, 2016/06/21 16:14:15]

Done.

+  handler.reset(new ReplacingResourceHandler(std::move(handler), this,
+                                             plugin_service, request));
 
   ScopedVector<ResourceThrottle> throttles;
 
   // Add a NavigationResourceThrottle for navigations.
   // PlzNavigate: the throttle is unnecessary as communication with the UI
   // thread is handled by the NavigationURLloader.
   if (!IsBrowserSideNavigationEnabled() && IsResourceTypeFrame(resource_type))
     throttles.push_back(new NavigationResourceThrottle(request, delegate()));
 
   if (delegate_) {
@@ skipping 11 matching lines @@
   }
 
   // TODO(ricea): Stop looking this up so much.
   ResourceRequestInfoImpl* info = ResourceRequestInfoImpl::ForRequest(request);
   throttles.push_back(scheduler_->ScheduleRequest(child_id, route_id,
                                                   info->IsAsync(), request));
 
   handler.reset(new ThrottlingResourceHandler(std::move(handler), request,
                                               std::move(throttles)));
 
+  // Insert a buffered event handler to sniff the mime type first.
+  handler.reset(new MimeTypeResourceHandler(std::move(handler), request));
+
   return handler;
 }
 
 void ResourceDispatcherHostImpl::OnReleaseDownloadedFile(int request_id) {
   UnregisterDownloadedTempFile(filter_->child_id(), request_id);
 }
 
 void ResourceDispatcherHostImpl::OnDidChangePriority(
     int request_id,
     net::RequestPriority new_priority,
@@ skipping 921 matching lines @@
   ssl.cert_id = GetCertStore()->StoreCert(ssl_info.cert.get(), child_id);
   response->head.security_info = SerializeSecurityInfo(ssl);
 }
 
 CertStore* ResourceDispatcherHostImpl::GetCertStore() {
   return cert_store_for_testing_ ? cert_store_for_testing_
                                  : CertStore::GetInstance();
 }
 
 }  // namespace content