Change dart:io Platform.script to return a URI. Change all uses of Platform.script to work with th…

tests/standalone/io/http_proxy_test.dart

Index: tests/standalone/io/http_proxy_test.dart
diff --git a/tests/standalone/io/http_proxy_test.dart b/tests/standalone/io/http_proxy_test.dart
index 81806ab65c2c49b88ab17ba2bf85198b1979d41e..d8f59ad00ecc4985fe4fd89a65bb420ade6e3011 100644
--- a/tests/standalone/io/http_proxy_test.dart
+++ b/tests/standalone/io/http_proxy_test.dart
@@ -746,7 +746,7 @@ void testRealProxyAuth() {
 }
 
 void InitializeSSL() {
-  var testPkcertDatabase = join(dirname(Platform.script), 'pkcert');
+  var testPkcertDatabase = Platform.script.resolve('pkcert').toFilePath();
   SecureSocket.initialize(database: testPkcertDatabase,
                           password: 'dartdart');
 }