Add debug mirror support for ES6 Map/Set iterators.

test/mjsunit/es6/mirror-iterators.js

+// Copyright 2014 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
+// Test the mirror object for collection iterators.
+
+function testIteratorMirror(iter, offset, expected) {
+  while (offset-- > 0) iter.next();
+
+  var mirror = debug.MakeMirror(iter);
+  assertTrue(mirror.isIterator());
+
+  var preview = mirror.preview();
+  assertArrayEquals(expected, preview);
+
+  // Check that iterator has not changed after taking preview.
+  var values = [];
+  for (var i of iter) values.push(i);
+  assertArrayEquals(expected, values);
+}
+
+var o1 = { foo: 1 };
+var o2 = { foo: 2 };
+
+var map = new Map();
+map.set(41, 42);
+map.set(o1, o2);
+
+testIteratorMirror(map.keys(), 0, [41, o1]);
+testIteratorMirror(map.values(), 0, [42, o2]);
+testIteratorMirror(map.entries(), 0, [[41, 42], [o1, o2]]);
+
+testIteratorMirror(map.keys(), 1, [o1]);
+testIteratorMirror(map.values(), 1, [o2]);
+testIteratorMirror(map.entries(), 1, [[o1, o2]]);
+
+testIteratorMirror(map.keys(), 2, []);
+testIteratorMirror(map.values(), 2, []);
+testIteratorMirror(map.entries(), 2, []);
+
+var set = new Set();
+set.add(41);
+set.add(42);
+set.add(o1);
+set.add(o2);
+
+testIteratorMirror(set.keys(), 0, [41, 42, o1, o2]);
+testIteratorMirror(set.values(), 0, [41, 42, o1, o2]);
+testIteratorMirror(set.entries(), 0, [[41, 41], [42, 42], [o1, o1], [o2, o2]]);
+
+testIteratorMirror(set.keys(), 1, [42, o1, o2]);
+testIteratorMirror(set.values(), 1, [42, o1, o2]);
+testIteratorMirror(set.entries(), 1, [[42, 42], [o1, o1], [o2, o2]]);
+
+testIteratorMirror(set.keys(), 3, [o2]);
+testIteratorMirror(set.values(), 3, [o2]);
+testIteratorMirror(set.entries(), 3, [[o2, o2]]);
+
+testIteratorMirror(set.keys(), 5, []);
+testIteratorMirror(set.values(), 5, []);
+testIteratorMirror(set.entries(), 5, []);