Use dartfmt on Observatory code

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

Index: runtime/observatory/lib/src/repositories/top_retaining_instances.dart
diff --git a/runtime/observatory/lib/src/repositories/top_retaining_instances.dart b/runtime/observatory/lib/src/repositories/top_retaining_instances.dart
index 117c679763051d09a36605f55f450d55a40b4840..00947622496e783a81bbff5e049b4bf552971823 100644
--- a/runtime/observatory/lib/src/repositories/top_retaining_instances.dart
+++ b/runtime/observatory/lib/src/repositories/top_retaining_instances.dart
@@ -14,9 +14,8 @@ class TopRetainingInstancesRepository
     final raw = await isolate.fetchHeapSnapshot(true).last;
     final snapshot = new HeapSnapshot();
     await snapshot.loadProgress(isolate, raw).last;
-    return (await Future.wait(snapshot.getMostRetained(isolate,
-                                                      classId: cls.vmCid,
-                                                      limit: 10)))
-           .map((object) => new S.RetainingObject(object));
+    return (await Future.wait(
+            snapshot.getMostRetained(isolate, classId: cls.vmCid, limit: 10)))
+        .map((object) => new S.RetainingObject(object));
   }
 }