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

tests/standalone/io/process_stdout_test.dart

Index: tests/standalone/io/process_stdout_test.dart
diff --git a/tests/standalone/io/process_stdout_test.dart b/tests/standalone/io/process_stdout_test.dart
index 79b3fedcc20cd594b62d191e57d409ee453a2df3..366cc022879223a8e9736d76f548378c721e7309 100644
--- a/tests/standalone/io/process_stdout_test.dart
+++ b/tests/standalone/io/process_stdout_test.dart
@@ -9,10 +9,10 @@
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
-#import("dart:io");
-#import("dart:math");
+import "dart:io";
+import "dart:math";
 
-#source("process_test_util.dart");
+part "process_test_util.dart";
 
 void test(Future<Process> future, int expectedExitCode) {
   future.then((process) {