service worker: Clarify the navigation preload network error message.

third_party/WebKit/Source/web/ServiceWorkerGlobalScopeProxy.cpp

Index: third_party/WebKit/Source/web/ServiceWorkerGlobalScopeProxy.cpp
diff --git a/third_party/WebKit/Source/web/ServiceWorkerGlobalScopeProxy.cpp b/third_party/WebKit/Source/web/ServiceWorkerGlobalScopeProxy.cpp
index a03713f246686e97e800801ab06aefd3cecc78ba..c7e8b5b33844e27bd80aced8b8bb71899f7eec8f 100644
--- a/third_party/WebKit/Source/web/ServiceWorkerGlobalScopeProxy.cpp
+++ b/third_party/WebKit/Source/web/ServiceWorkerGlobalScopeProxy.cpp
@@ -310,6 +310,13 @@ void ServiceWorkerGlobalScopeProxy::OnNavigationPreloadError(
   // This method may be called after onNavigationPreloadResponse() was called.
   if (!fetch_event)
     return;
+  // Display an unsanitized console message.
+  if (!error->unsanitized_message.IsEmpty()) {
+    WorkerGlobalScope()->AddConsoleMessage(ConsoleMessage::Create(
+        kWorkerMessageSource, blink::MessageLevel::kErrorMessageLevel,
+        error->unsanitized_message));
+  }
+  // Reject the preloadResponse promise.
   fetch_event->OnNavigationPreloadError(
       WorkerGlobalScope()->ScriptController()->GetScriptState(),
       std::move(error));