Uncomment and clean up engine_test.dart

pkg/analyzer/lib/src/generated/java_core.dart

 library java.core;
 
 import "dart:math" as math;
 
 final Stopwatch nanoTimeStopwatch = new Stopwatch();
 
 const int LONG_MAX_VALUE = 0x7fffffffffffffff;
 
 class JavaSystem {
   static int currentTimeMillis() {
@@ skipping 317 matching lines @@
 class NoSuchElementException extends JavaException {
   String toString() => "NoSuchElementException";
 }
 
 class NumberFormatException extends JavaException {
   String toString() => "NumberFormatException";
 }
 
 /// Parses given string to [Uri], throws [URISyntaxException] if invalid.
 Uri parseUriWithException(String str) {
-  Uri uri = Uri.parse(str);
+  Uri uri;
+  try {
+    uri = Uri.parse(str);
+  } on FormatException catch (e) {
+    throw new URISyntaxException(e.toString());
+  }
   if (uri.path.isEmpty) {
-    throw new URISyntaxException();
+    throw new URISyntaxException('empty path');
   }
   return uri;
 }
 
 class URISyntaxException implements Exception {
-  String toString() => "URISyntaxException";
+  final String message;
+  URISyntaxException(this.message);
+  String toString() => "URISyntaxException: $message";
 }
 
 class MissingFormatArgumentException implements Exception {
   final String s;
 
   String toString() => "MissingFormatArgumentException: $s";
 
   MissingFormatArgumentException(this.s);
 }
 
@@ skipping 182 matching lines @@
  *     format('{0} are you {1}ing?', ['What', 'read']) = 'What are you reading?'
  */
 String formatList(String pattern, List args) {
   return pattern.replaceAllMapped(new RegExp(r'\{(\d+)\}'), (match) {
     String indexStr = match.group(1);
     int index = int.parse(indexStr);
     var arg = args[index];
     return arg != null ? arg.toString() : null;
   });
 }