Use dartfmt on Observatory code

runtime/observatory/lib/src/repositories/retaining_path.dart

Index: runtime/observatory/lib/src/repositories/retaining_path.dart
diff --git a/runtime/observatory/lib/src/repositories/retaining_path.dart b/runtime/observatory/lib/src/repositories/retaining_path.dart
index 1ff9835dd0e02125925e440877afd037eeca815c..68253f795d91b90e12bbb89ad88f97f7a7eba7d7 100644
--- a/runtime/observatory/lib/src/repositories/retaining_path.dart
+++ b/runtime/observatory/lib/src/repositories/retaining_path.dart
@@ -8,10 +8,8 @@ class RetainingPathRepository implements M.RetainingPathRepository {
   Future<M.RetainingPath> get(M.IsolateRef i, String id) async {
     S.Isolate isolate = i as S.Isolate;
     assert(isolate != null);
-    final response = await isolate.invokeRpc('_getRetainingPath', {
-        'targetId' : id,
-        'limit': 100
-    });
+    final response = await isolate
+        .invokeRpc('_getRetainingPath', {'targetId': id, 'limit': 100});
     return new S.RetainingPath(response);
   }
 }