Add test for 2.1 CanonicalizeLocaleList ( locales ) (#2040)

See https://tc39.github.io/proposal-intl-locale/#sec-canonicalizelocalelist

test/intl402/Locale/canonicalize-locale-list-take-locale.js

@@ -0,0 +1,53 @@
+// Copyright 2019 Google Inc.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-intl.locale
+description: >
+    Verifies CanonicalizeLocaleList will take Intl.Locale as locales.
+info: |
+    CanonicalizeLocaleList ( locales )
+    3. If Type(locales) is String or locales has an [[InitializedLocale]] internal slot, then
+       a. Let O be CreateArrayFromList(« locales »).
+
+       c. iii. If Type(kValue) is Object and kValue has an [[InitializedLocale]] internal slot, then
+            1. Let tag be kValue.[[Locale]].
+          iv. Else,
+            1. Let tag be ? ToString(kValue).
+features: [Intl.Locale]
+---*/
+
+const tag = "ar";
+const tag2 = "fa";
+const tag3 = "zh";
+const loc = new Intl.Locale(tag);
+
+// Monkey-patching Intl.Locale
+class PatchedLocale extends Intl.Locale {
+  constructor(tag, options) {
+    super(tag, options);
+  }
+  toString() {
+    // this should NOT get called.
+    assert(false, "toString should not be called")
+  }
+}
+const ploc = new PatchedLocale(tag2);
+
+// Test Intl.Locale as the only argument
+let res = Intl.getCanonicalLocales(loc);
+assert.sameValue(res.length, 1);
+assert.sameValue(res[0], tag);
+
+// Test Monkey-patched Intl.Locale as the only argument
+res = Intl.getCanonicalLocales(ploc);
+assert.sameValue(res.length, 1);
+assert.sameValue(res[0], tag2);
+
+// Test Intl.Locale and the Monkey-patched one are in
+// array.
+res = Intl.getCanonicalLocales([loc, tag3, ploc]);
+assert.sameValue(res.length, 3);
+assert.sameValue(res[0], tag);
+assert.sameValue(res[1], tag3);
+assert.sameValue(res[2], tag2);