Add an error page for HTTP 404 error pages without bodies.

extensions/browser/api/runtime/runtime_apitest.cc

Index: extensions/browser/api/runtime/runtime_apitest.cc
diff --git a/extensions/browser/api/runtime/runtime_apitest.cc b/extensions/browser/api/runtime/runtime_apitest.cc
index 78f5998cffdfeb6d73146667599f22e28ffcdfc1..9d80bca2754decac37a743f3d85455927f4fbd14 100644
--- a/extensions/browser/api/runtime/runtime_apitest.cc
+++ b/extensions/browser/api/runtime/runtime_apitest.cc
@@ -25,10 +25,10 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, ChromeRuntimeUnprivileged) {
   ASSERT_TRUE(
       LoadExtension(test_data_dir_.AppendASCII("runtime/content_script")));
 
-  // The content script runs on webpage.html.
+  // The content script runs on this page.
   extensions::ResultCatcher catcher;
   ui_test_utils::NavigateToURL(browser(),
-                               embedded_test_server()->GetURL("/webpage.html"));
+                               embedded_test_server()->GetURL("/echo"));
   EXPECT_TRUE(catcher.GetNextResult()) << message_;
 }