vm-service: Add optional 'scope' parameter to 'evaluate' and 'evaluateInFrame'.

runtime/observatory/tests/service/evaluate_with_scope_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:async';
+import 'dart:developer';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'service_test_common.dart';
+import 'test_helper.dart';
+
+var thing1;
+var thing2;
+
+testeeMain() {
+  thing1 = 3;
+  thing2 = 4;
+}
+
+var tests = [
+  (Isolate isolate) async {
+    var lib = await isolate.rootLibrary.load();
+    var thing1 =
+        (await lib.variables.singleWhere((v) => v.name == "thing1").load())
+            .staticValue;
+    print(thing1);
+    var thing2 =
+        (await lib.variables.singleWhere((v) => v.name == "thing2").load())
+            .staticValue;
+    print(thing2);
+
+    var result = await lib.evaluate("x + y", scope: {"x": thing1, "y": thing2});
+    expect(result.valueAsString, equals('7'));
+
+    bool didThrow = false;
+    try {
+      result = await lib.evaluate("x + y", scope: {"x": lib, "y": lib});
+      print(result);
+    } catch (e) {
+      didThrow = true;
+      expect(e.toString(),
+          contains("Cannot evaluate against a VM-internal object"));
+    }
+    expect(didThrow, isTrue);
+
+    didThrow = false;
+    try {
+      result =
+          await lib.evaluate("x + y", scope: {"not&an&identifier": thing1});
+      print(result);
+    } catch (e) {
+      didThrow = true;
+      expect(e.toString(), contains("invalid 'scope' parameter"));
+    }
+    expect(didThrow, isTrue);
+  },
+];
+
+main(args) => runIsolateTests(args, tests, testeeBefore: testeeMain);