Address observatory analysis issues.

runtime/observatory/tests/service/get_native_allocation_samples_test.dart

 // Copyright (c) 2017, 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 'package:observatory/cpu_profile.dart';
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/service_io.dart';
-import 'package:observatory/cpu_profile.dart';
 import 'package:unittest/unittest.dart';
-import 'service_test_common.dart';
+
 import 'test_helper.dart';
 
 void verifyHelper(var root, bool exclusive) {
   if (root.children.length == 0) {
     return;
   }
 
 /*  if (!(root is FunctionCallTreeNode)) {
     print('${root.profileCode.code.name}');
   } else {
@@ skipping 54 matching lines @@
     var codeTreeExclusive =
         cpuProfile.loadCodeTree(M.ProfileTreeDirection.exclusive);
     var functionTreeExclusive =
         cpuProfile.loadFunctionTree(M.ProfileTreeDirection.exclusive);
     verify(codeTreeExclusive, true);
     verify(functionTreeExclusive, true);
   }
 ];
 
 main(args) async => runVMTests(args, tests);