Do not sniff mime type for fetch() requests

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 50 matching lines @@
   scoped_refptr<net::IOBuffer> buf_;
 };
 
 }  // namespace
 
 MimeSniffingResourceHandler::MimeSniffingResourceHandler(
     std::unique_ptr<ResourceHandler> next_handler,
     ResourceDispatcherHostImpl* host,
     PluginService* plugin_service,
     InterceptingResourceHandler* intercepting_handler,
-    net::URLRequest* request)
+    net::URLRequest* request,
+    RequestContextType request_context_type)
     : LayeredResourceHandler(request, std::move(next_handler)),
       state_(STATE_STARTING),
       host_(host),
 #if defined(ENABLE_PLUGINS)
       plugin_service_(plugin_service),
 #endif
       must_download_(false),
       must_download_is_set_(false),
       read_buffer_size_(0),
       bytes_read_(0),
       intercepting_handler_(intercepting_handler),
+      request_context_type_(request_context_type),
       weak_ptr_factory_(this) {
 }
 
 MimeSniffingResourceHandler::~MimeSniffingResourceHandler() {}
 
 void MimeSniffingResourceHandler::SetController(
     ResourceController* controller) {
   ResourceHandler::SetController(controller);
 
   // Downstream handlers see the MimeSniffingResourceHandler as their
@@ skipping 42 matching lines @@
   request()->SetExtraRequestHeaderByName(kAcceptHeader, accept_value, false);
   return next_handler_->OnWillStart(url, defer);
 }
 
 bool MimeSniffingResourceHandler::OnResponseStarted(ResourceResponse* response,
                                                     bool* defer) {
   DCHECK_EQ(STATE_STARTING, state_);
   response_ = response;
 
   state_ = STATE_BUFFERING;
-
   // A 304 response should not contain a Content-Type header (RFC 7232 section
   // 4.1). The following code may incorrectly attempt to add a Content-Type to
   // the response, and so must be skipped for 304 responses.
   if (!(response_->head.headers.get() &&
         response_->head.headers->response_code() == 304)) {
     if (ShouldSniffContent())
       return true;
 
     if (response_->head.mime_type.empty()) {
       // Ugg.  The server told us not to sniff the content but didn't give us a
@@ skipping 163 matching lines @@
   bool result = next_handler_->OnReadCompleted(bytes_read_, defer);
 
   read_buffer_ = nullptr;
   read_buffer_size_ = 0;
   bytes_read_ = 0;
 
   return result;
 }
 
 bool MimeSniffingResourceHandler::ShouldSniffContent() {
+  if (request_context_type_ == REQUEST_CONTEXT_TYPE_FETCH) {
+    // MIME sniffing should be disabled for a request initiated by fetch().
+    return false;
+  }
+
   const std::string& mime_type = response_->head.mime_type;
 
   std::string content_type_options;
   request()->GetResponseHeaderByName("x-content-type-options",
                                      &content_type_options);
 
   bool sniffing_blocked =
       base::LowerCaseEqualsASCII(content_type_options, "nosniff");
   bool we_would_like_to_sniff =
       net::ShouldSniffMimeType(request()->url(), mime_type);
@@ skipping 169 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