Bug 1127827, part 3 - Weak map get should always return undefined on failure to find the key. r=Waldo,jgraham

dom/imptests/failures/html/js/builtins/test_WeakMap.prototype-properties.html.json

@@ -2,7 +2,6 @@
   "WeakMap.prototype.clear.length": true,
   "WeakMap.prototype.delete.length": true,
   "WeakMap.prototype.get.length": true,
-  "WeakMap.prototype.get: return undefined": true,
   "WeakMap.prototype.has.length": true,
   "WeakMap.prototype.set.length": true
 }

js/src/jsweakmap.cpp

@@ -274,7 +274,7 @@ WeakMap_get_impl(JSContext *cx, CallArgs args)
         }
     }
 
-    args.rval().set((args.length() > 1) ? args[1] : UndefinedValue());
+    args.rval().setUndefined();
     return true;
 }
 

js/src/tests/js1_8_5/extensions/weakmap.js

@@ -87,7 +87,7 @@ function test()
     check(function() map.set(key, 42) === map);
     check(function() map.get(key) == 42);
     check(function() typeof map.get({}) == "undefined");
-    check(function() map.get({}, "foo") == "foo");
+    check(function() map.get({}, "foo") == undefined);
 
     gc(); gc(); gc();
 

testing/web-platform/meta/js/builtins/WeakMap.prototype-properties.html.ini

@@ -1,8 +1,6 @@
 [WeakMap.prototype-properties.html]
   type: testharness
+
   [WeakMap.prototype.get.length]
     expected: FAIL
 
-  [WeakMap.prototype.get: return undefined]
-    expected: FAIL
-