Issue 20520. JavaFile.toURI() should use absolute path.

editor/util/plugins/com.google.dart.java2dart/resources/java_io.dart

 library java.io;
 
 import "dart:io";
 import 'java_core.dart' show JavaIOException, CharSequence;
 import 'package:path/path.dart' as pathos;
 
 class JavaSystemIO {
   static Map<String, String> _properties = new Map();
   static String getProperty(String name) {
     {
@@ skipping 94 matching lines @@
   }
   bool isExecutable() {
     return _newFile().statSync().mode & 0x111 != 0;
   }
   bool isFile() {
     return _newFile().existsSync();
   }
   bool isDirectory() {
     return _newDirectory().existsSync();
   }
-  Uri toURI() => pathos.toUri(_path);
+  Uri toURI() {
+    String path = getAbsolutePath();
+    return pathos.toUri(path);
+  }
   String readAsStringSync() => _newFile().readAsStringSync();
   int lastModified() {
     if (!_newFile().existsSync()) return 0;
     return _newFile().lastModifiedSync().millisecondsSinceEpoch;
 
   }
   List<JavaFile> listFiles() {
     var files = <JavaFile>[];
     var entities = _newDirectory().listSync();
     for (FileSystemEntity entity in entities) {
       files.add(new JavaFile(entity.path));
     }
     return files;
   }
   File _newFile() => new File(_path);
   Directory _newDirectory() => new Directory(_path);
 }