Run dartfmt on all files under runtime.

runtime/observatory/tests/observatory_ui/mocks/objects/heap_space.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.
 
 part of mocks;
 
 class HeapSpaceMock implements M.HeapSpace {
   final int used;
   final int capacity;
   final int collections;
   final int external;
   final Duration avgCollectionTime;
   final Duration totalCollectionTime;
   final Duration avgCollectionPeriod;
-  const HeapSpaceMock({this.used: 0, this.capacity: 1, this.collections: 0,
-                       this.external: 1,
-                       this.avgCollectionTime: const Duration(),
-                       this.totalCollectionTime: const Duration(),
-                       this.avgCollectionPeriod: const Duration()});
+  const HeapSpaceMock(
+      {this.used: 0,
+      this.capacity: 1,
+      this.collections: 0,
+      this.external: 1,
+      this.avgCollectionTime: const Duration(),
+      this.totalCollectionTime: const Duration(),
+      this.avgCollectionPeriod: const Duration()});
 }