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

tests/compiler/dart2js/package_root_test.dart

Index: tests/compiler/dart2js/package_root_test.dart
diff --git a/tests/compiler/dart2js/package_root_test.dart b/tests/compiler/dart2js/package_root_test.dart
index 3b74c0924de928f69f42f559b8337228458a0857..6ff118f71021156ac52efb50e2ab079b6981183a 100644
--- a/tests/compiler/dart2js/package_root_test.dart
+++ b/tests/compiler/dart2js/package_root_test.dart
@@ -31,7 +31,7 @@ main() {}
 };
 
 void runCompiler(Uri main) {
-  Uri script = currentDirectory.resolve(nativeToUriPath(Platform.script));
+  Uri script = currentDirectory.resolveUri(Platform.script);
   Uri libraryRoot = script.resolve('../../../sdk/');
 
   var provider = new MemorySourceFileProvider(MEMORY_SOURCE_FILES);