Merge pull request #128 from w3c/jgraham/manifest_order

Ensure that manifests are always run in the same order; r=Ms2ger

wptrunner/testloader.py

@@ -496,7 +496,7 @@ def load_metadata(self, test_manifest, metadata_path, test_path):
     def iter_tests(self):
         manifest_items = []
 
-        for manifest in self.manifests.keys():
+        for manifest in sorted(self.manifests.keys()):
             manifest_iter = iterfilter(self.manifest_filters,
                                        manifest.itertypes(*self.test_types))
             manifest_items.extend(manifest_iter)