Bug 1317101 - Part 8a: Read defaults from ancestor manifests when processing test metadata. r=chmanchester

MozReview-Commit-ID: 90ldX6DuKBy

--HG--
extra : rebase_source : 52827e9088422bc267441d6c1b9b4f78879f5c59
extra : histedit_source : 327525467a30a9670b29686e8f66dbeb449f2081

python/mozbuild/mozbuild/testing.py

@@ -65,11 +65,17 @@ class TestMetadata(object):
         for path, tests in test_data.items():
             for metadata in tests:
                 if defaults:
-                    manifest = metadata['manifest']
-                    manifest_defaults = defaults.get(manifest)
-                    if manifest_defaults:
-                        metadata = manifestparser.combine_fields(manifest_defaults,
-                                                                 metadata)
+                    defaults_manifests = [metadata['manifest']]
+
+                    ancestor_manifest = metadata.get('ancestor-manifest')
+                    if ancestor_manifest:
+                        defaults_manifests.append(ancestor_manifest)
+
+                    for manifest in defaults_manifests:
+                        manifest_defaults = defaults.get(manifest)
+                        if manifest_defaults:
+                            metadata = manifestparser.combine_fields(manifest_defaults,
+                                                                     metadata)
                 self._tests_by_path[path].append(metadata)
                 self._test_dirs.add(os.path.dirname(path))
                 flavor = metadata.get('flavor')