Remove old #import, #source, and #library syntax from tests/standalone.

tests/standalone/io/http_connection_header_test.dart

Index: tests/standalone/io/http_connection_header_test.dart
diff --git a/tests/standalone/io/http_connection_header_test.dart b/tests/standalone/io/http_connection_header_test.dart
index ead20673abe9b9b1252d20be91ac56ed6de2736d..03c7d93403d031731c6889772af293d30c119c96 100644
--- a/tests/standalone/io/http_connection_header_test.dart
+++ b/tests/standalone/io/http_connection_header_test.dart
@@ -3,8 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 //
 
-#import("dart:isolate");
-#import("dart:io");
+import "dart:isolate";
+import "dart:io";
 
 void setConnectionHeaders(HttpHeaders headers) {
   headers.add(HttpHeaders.CONNECTION, "my-connection-header1");