Make js_ast test line-ending agnostic.

pkg/js_ast/test/printer_callback_test.dart

Index: pkg/js_ast/test/printer_callback_test.dart
diff --git a/pkg/js_ast/test/printer_callback_test.dart b/pkg/js_ast/test/printer_callback_test.dart
index b4ff074256cf273ad87d82e8bb522ba705322748..e4bcf835d2f36f4c14cd0771bd27a0a04ee3edc1 100644
--- a/pkg/js_ast/test/printer_callback_test.dart
+++ b/pkg/js_ast/test/printer_callback_test.dart
@@ -105,11 +105,15 @@ void check(Map<TestMode, String> map) {
   map.forEach((TestMode mode, String expectedOutput) {
     Context context = new Context(mode);
     new Printer(options, context).visit(node);
-    expect(context.getText(), equals(expectedOutput),
+    expect(context.getText(),
+        equals(canonicalizeLineEndings(expectedOutput)),
         reason: "Unexpected output for $code in $mode");
   });
 }
 
+// The string literals may end in \r\n or \n depending on filesystem.
+canonicalizeLineEndings(String s) => s.replaceAll('\r\n', '\n');
+
 class Context extends SimpleJavaScriptPrintingContext {
   final TestMode mode;
   final Map<Node, int> idMap = {};