[debug] add test case for scope iterator using correct language mode.

test/mjsunit/regress/regress-5207.js

+// Copyright 2012 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-debug-as debug
+
+'use strict';
+var Debug = debug.Debug;
+var exception = null;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    var scopes = exec_state.frame(0).allScopes();
+    assertEquals(debug.ScopeType.Eval, scopes[0].scopeType());
+    assertEquals(1, scopes[0].scopeObject().value().a);
+    assertEquals(debug.ScopeType.Script, scopes[1].scopeType());
+    assertEquals(undefined, scopes[1].scopeObject().value().a);
+    assertEquals(debug.ScopeType.Global, scopes[2].scopeType());
+    assertEquals(undefined, scopes[2].scopeObject().value().a);
+  } catch (e) {
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+// Eval inherits strict mode.
+eval("var a = 1; debugger;");
+Debug.setListener(null);
+assertNull(exception);