Run dartfmt on all files under runtime.

runtime/observatory/tests/service/object_graph_stack_reference_test.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // VMOptions=--error_on_bad_type --error_on_bad_override
 
 import 'dart:developer';
 
 import 'test_helper.dart';
 import 'service_test_common.dart';
 
 import 'package:observatory/heap_snapshot.dart';
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/object_graph.dart';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 
 int arrayLength = 1024 * 1024;
 int minArraySize = arrayLength * 4;
 
 void script() {
   var stackSlot = new List(arrayLength);
   debugger();
-  print(stackSlot);  // Prevent optimizing away the stack slot.
+  print(stackSlot); // Prevent optimizing away the stack slot.
 }
 
 checkForStackReferent(Isolate isolate) async {
   Library corelib =
       isolate.libraries.singleWhere((lib) => lib.uri == 'dart:core');
   await corelib.load();
   Class _List =
       corelib.classes.singleWhere((cls) => cls.vmName.startsWith('_List'));
   int kArrayCid = _List.vmCid;
 
   RawHeapSnapshot raw =
       await isolate.fetchHeapSnapshot(M.HeapSnapshotRoots.user, false).last;
   HeapSnapshot snapshot = new HeapSnapshot();
   await snapshot.loadProgress(isolate, raw).last;
   ObjectGraph graph = snapshot.graph;
 
   var root = graph.root;
-  var stack = graph.root.dominatorTreeChildren()
-      .singleWhere((child) => child.isStack);
+  var stack =
+      graph.root.dominatorTreeChildren().singleWhere((child) => child.isStack);
   expect(stack.retainedSize, greaterThanOrEqualTo(minArraySize));
 
   bool foundBigArray = false;
   for (var stackReferent in stack.dominatorTreeChildren()) {
     if (stackReferent.vmCid == kArrayCid &&
         stackReferent.shallowSize >= minArraySize) {
       foundBigArray = true;
     }
   }
 }
 
 var tests = [
   hasStoppedAtBreakpoint,
   checkForStackReferent,
   resumeIsolate,
 ];
 
 main(args) => runIsolateTests(args, tests, testeeConcurrent: script);