Implement --dump-info for batch mode.

bin/dartdevc.dart

Index: bin/dartdevc.dart
diff --git a/bin/dartdevc.dart b/bin/dartdevc.dart
index 61e306aad185f3c713a453129ee91e1f922d21de..df365eb467a3b9c174871fa30aa2ca724f070661 100755
--- a/bin/dartdevc.dart
+++ b/bin/dartdevc.dart
@@ -25,7 +25,7 @@ void _showUsageAndExit() {
   exit(1);
 }
 
-main(List<String> args) async {
+main(List<String> args) {
   var options;
 
   try {
@@ -46,7 +46,6 @@ main(List<String> args) async {
   if (options.serverMode) {
     new DevServer(options).start();
   } else {
-    var success = compile(options);
-    exit(success ? 0 : 1);
+    exit(compile(options) ? 0 : 1);
   }
 }