Make parser and scanner suites able to run standalone.

pkg/front_end/test/fasta/parser/parser_suite.dart

Index: pkg/front_end/test/fasta/parser/parser_suite.dart
diff --git a/pkg/front_end/test/fasta/parser/parser_suite.dart b/pkg/front_end/test/fasta/parser/parser_suite.dart
index 1ac6b2bb85542f71eaace0ba428c6c00fd66c5b4..6e710a0f5064e236518c2089fe1c4f08bf337d84 100644
--- a/pkg/front_end/test/fasta/parser/parser_suite.dart
+++ b/pkg/front_end/test/fasta/parser/parser_suite.dart
@@ -17,9 +17,9 @@ Future<ChainContext> createContext(
 
 class ScannerContext extends ChainContext {
   final List<Step> steps = const <Step>[
-      const Read(),
-      const Scan(),
-      const Parse(),
+    const Read(),
+    const Scan(),
+    const Parse(),
   ];
 }
 
@@ -28,8 +28,7 @@ class Parse extends Step<ScannerResult, Null, ChainContext> {
 
   String get name => "parse";
 
-  Future<Result<Null>> run(
-      ScannerResult result, ChainContext context) async {
+  Future<Result<Null>> run(ScannerResult result, ChainContext context) async {
     try {
       List<ParserError> errors = parse(result.tokens);
       if (errors.isNotEmpty) {
@@ -42,4 +41,5 @@ class Parse extends Step<ScannerResult, Null, ChainContext> {
   }
 }
 
-main(List<String> arguments) => runMe(arguments, createContext);
+main(List<String> arguments) =>
+    runMe(arguments, createContext, "../testing.json");