ES6: Add support for Set and Map clear method

test/mjsunit/harmony/collections.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 337 matching lines @@
 var m = new Map();
 assertFalse(m.hasOwnProperty('size'));
 for (var i = 0; i < 10; i++) {
   assertEquals(i, m.size);
   m.set(i, i);
 }
 for (var i = 9; i >= 0; i--) {
   m.delete(i);
   assertEquals(i, m.size);
 }
+
+// Test clear
+var a = new Set();
+s.add(42);
+assertTrue(s.has(42));
+s.clear();
+assertFalse(s.has(42));
+assertEquals(0, s.size);
+
+var m = new Map();
+m.set(42, true);
+assertTrue(m.has(42));
+m.clear();
+assertFalse(m.has(42));
+assertEquals(0, m.size);