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

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

Index: editor/util/plugins/com.google.dart.java2dart/resources/java_io.dart
diff --git a/editor/util/plugins/com.google.dart.java2dart/resources/java_io.dart b/editor/util/plugins/com.google.dart.java2dart/resources/java_io.dart
index 347463b9bd10f285d371bb00ccf2bf89b33eb84e..245bd04fdc3be12ecff0c30f4e4a89a9c184d778 100644
--- a/editor/util/plugins/com.google.dart.java2dart/resources/java_io.dart
+++ b/editor/util/plugins/com.google.dart.java2dart/resources/java_io.dart
@@ -112,7 +112,10 @@ class JavaFile {
   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;