Ensure the debugger considers parameters to be in scope at the method entry debug step.

runtime/observatory/tests/service/parameters_in_scope_at_entry_test.dart

+// Copyright (c) 2015, 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  --verbose_debug
+
+import 'package:observatory/service_io.dart';
+import 'test_helper.dart';
+import 'dart:developer';
+import 'package:unittest/unittest.dart';
+
+foo(param) {
+  return param;
+}
+
+fooClosure() {
+  theClosureFunction(param) {
+    return param;
+  }
+  return theClosureFunction;
+}
+
+testMain() {
+  debugger();
+  foo("in-scope");  // Line 24
+
+  var f = fooClosure();
+  debugger();
+  f("in-scope");  // Line 28
+}
+
+var tests = [
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(24),
+  (isolate) => isolate.stepInto(),
+  hasStoppedAtBreakpoint,
+  (isolate) async {
+    var stack = await isolate.getStack();
+    Frame top = stack['frames'][0];
+    print(top);
+    expect(top.function.name, equals("foo"));
+    print(top.variables);
+    expect(top.variables.length, equals(1));
+    var param = top.variables[0];
+    expect(param['name'], equals("param"));
+    expect(param['value'].valueAsString, equals("in-scope"));
+  },
+  resumeIsolate,
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(28),
+  (isolate) => isolate.stepInto(),
+  hasStoppedAtBreakpoint,
+  (isolate) async {
+    var stack = await isolate.getStack();
+    Frame top = stack['frames'][0];
+    print(top);
+    expect(top.function.name, equals("theClosureFunction"));
+    print(top.variables);
+    expect(top.variables.length, equals(1));
+    var param = top.variables[0];
+    expect(param['name'], equals("param"));
+    expect(param['value'].valueAsString, equals("in-scope"));
+  },
+  resumeIsolate,
+];
+
+main(args) => runIsolateTests(args, tests, testeeConcurrent: testMain);