Move MimeTypeResourceHandler before ThrottlingResourceHandler

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index fb12a9b95407a2d9276c7bbe9279646f22f837d8..fb587bd22889f7dfa2f937eb7b1c5fafca5706d5 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -49,8 +49,9 @@
 #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/intercepting_resource_handler.h"
 #include "content/browser/loader/loader_delegate.h"
-#include "content/browser/loader/mime_type_resource_handler.h"
+#include "content/browser/loader/mime_sniffing_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"
@@ -1656,13 +1657,12 @@ ResourceDispatcherHostImpl::AddStandardHandlers(
     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 InterceptingResourceHandler will replace its next handler with an
+  // appropriate one based on the MIME type of the response if needed. It
+  // should be placed at the end of the chain, just before |handler|.
+  handler.reset(new InterceptingResourceHandler(std::move(handler), request));
+  InterceptingResourceHandler* intercepting_handler =
+      static_cast<InterceptingResourceHandler*>(handler.get());
 
   ScopedVector<ResourceThrottle> throttles;
 
@@ -1696,6 +1696,18 @@ ResourceDispatcherHostImpl::AddStandardHandlers(
   handler.reset(new ThrottlingResourceHandler(std::move(handler), request,
                                               std::move(throttles)));
 
+  PluginService* plugin_service = nullptr;
+#if defined(ENABLE_PLUGINS)
+  plugin_service = PluginService::GetInstance();
+#endif
+
+  // Insert a buffered event handler to sniff the mime type first.
+  // Note: all ResourceHandler following the MimeSniffingResourceHandler should
+  // expect OnWillRead to be called *before* OnResponseStarted as part of the
+  // mime sniffing process.
+  handler.reset(new MimeSniffingResourceHandler(
+      std::move(handler), this, plugin_service, intercepting_handler, request));
+
   return handler;
 }