Fix analyzer warnings in service tests

runtime/observatory/tests/service/evaluate_activation_test.dart

Index: runtime/observatory/tests/service/evaluate_activation_test.dart
diff --git a/runtime/observatory/tests/service/evaluate_activation_test.dart b/runtime/observatory/tests/service/evaluate_activation_test.dart
index 2f1739a43c0f80121b92005f95420f5154974463..23d551a38b6e4bd2be9045d3960fd336176ed72e 100644
--- a/runtime/observatory/tests/service/evaluate_activation_test.dart
+++ b/runtime/observatory/tests/service/evaluate_activation_test.dart
@@ -6,22 +6,26 @@
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
-import 'dart:async';
 
 import 'dart:math' as math;
 
 breakHere() {}
 
+use(dynamic v) => v;
+
 class C {
   var instVar = 1;
   static var classVar = 2;
 
   method(methodParam) {
     var methodTemp = 4;
+    use(methodTemp);
     [5].forEach((outerParam) {
       var outerTemp = 6;
+      use(outerTemp);
       [7].forEach((innerParam) {
         var innerTemp = 8;
+        use(innerTemp);
         breakHere();
       });
     });
@@ -29,10 +33,13 @@ class C {
 
   static method2(methodParam) {
     var methodTemp = 4;
+    use(methodTemp);
     [5].forEach((outerParam) {
       var outerTemp = 6;
+      use(outerTemp);
       [7].forEach((innerParam) {
         var innerTemp = 8;
+        use(innerTemp);
         breakHere();
       });
     });
@@ -40,16 +47,20 @@ class C {
 
   method3(methodParam) {
     var methodTemp = 4;
+    use(methodTemp);
     breakHere();
   }
 
   static var closureWithReturnedHome;
   method4(methodParam) {
     var methodTemp = 4;
+    use(methodTemp);
     [5].forEach((outerParam) {
       var outerTemp = 6;
+      use(outerTemp);
       closureWithReturnedHome = (innerParam) {
         var innerTemp = 8;
+        use(innerTemp);
         breakHere();
       };
     });
@@ -57,6 +68,8 @@ class C {
 }
 
 testMethod(Isolate isolate) async {
+  // silence analyzer.
+  expect(math.sqrt(4), equals(2));
   Library rootLib = await isolate.rootLib.load();
   ServiceFunction function =
       rootLib.functions.singleWhere((f) => f.name == 'breakHere');