Don't test namespaces in idlharness if not exposed

Instead, if a namespace is not exposed, test that there is no global
property of that name, similar to what we do with interfaces.

resources/idlharness.js

@@ -734,7 +734,7 @@ IdlArray.prototype.test = function()
 
     Object.getOwnPropertyNames(this.members).forEach(function(memberName) {
         var member = this.members[memberName];
-        if (!(member instanceof IdlInterface)) {
+        if (!(member instanceof IdlInterface || member instanceof IdlNamespace)) {
             return;
         }
 
@@ -3451,6 +3451,17 @@ IdlNamespace.prototype.test_self = function ()
 
 IdlNamespace.prototype.test = function ()
 {
+    // If the namespace object is not exposed, only test that. Members can't be
+    // tested either
+    if (!this.exposed) {
+        if (!this.untested) {
+            subsetTestByKey(this.name, test, function() {
+                assert_false(this.name in self, this.name + " namespace should not exist");
+            }.bind(this), this.name + " namespace: existence and properties of namespace object");
+        }
+        return;
+    }
+
     if (!this.untested) {
         this.test_self();
     }

resources/test/tests/functional/idlharness/IdlNamespace/test_operation.html

@@ -67,7 +67,12 @@
 namespace baz {
   DOMString LongStory(any hero, DOMString... details);
   DOMString ShortStory(DOMString... details);
-};`);
+};
+[Exposed=Worker]
+namespace Absent {
+  undefined Lies();
+};
+`);
 idlArray.test();
 </script>
 <script type="text/json" id="expected">
@@ -233,6 +238,12 @@
       "status_string": "PASS",
       "properties": {},
       "message": null
+    },
+    {
+      "name": "Absent namespace: existence and properties of namespace object",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
     }
   ],
   "type": "complete"