Do not sniff mime type for fetch() requests

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 21183c34ab6026001aeeccdfca30332555a1e1f1..602168363cdb5d39846e192ec5958791f4933152 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -1715,12 +1715,17 @@ ResourceDispatcherHostImpl::AddStandardHandlers(
   plugin_service = PluginService::GetInstance();
 #endif
 
-  // Insert a buffered event handler to sniff the mime type.
-  // 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));
+  if (fetch_request_context_type != REQUEST_CONTEXT_TYPE_FETCH) {
+    // fetch() ignores mime sniffing.

[tyoshino (SeeGerritForStatus), 2016/09/08 06:04:31]

place above the if

[yhirano, 2016/09/08 06:08:39]

Done.

+    //
+    // Insert a buffered event handler to sniff the mime type.
+    // 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));
+  }
 
   // Add the pre mime sniffing throttles.
   handler.reset(new ThrottlingResourceHandler(