Change directory owner listing to list joint owners together.

third_party/WebKit/Tools/Scripts/webkitpy/w3c/directory_owners_extractor.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/w3c/directory_owners_extractor.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/w3c/directory_owners_extractor.py b/third_party/WebKit/Tools/Scripts/webkitpy/w3c/directory_owners_extractor.py
index 024faccc4a3ee5f372cd03a67b9b12cc69bc8ab7..ba162bf8c41ccaa90deac9a6022d28b9284ed2f7 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/w3c/directory_owners_extractor.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/w3c/directory_owners_extractor.py
@@ -62,7 +62,8 @@ class DirectoryOwnersExtractor(object):
             changed_files: A list of file paths relative to the repository root.
 
         Returns:
-            A dict mapping owner email addresses to lists of owned directories.
+            A dict mapping tuples of owner email addresses to lists of
+            owned directories.
         """
         tests = [self.finder.layout_test_name(path) for path in changed_files]
         tests = [t for t in tests if t is not None]
@@ -71,6 +72,5 @@ class DirectoryOwnersExtractor(object):
             owned_tests = [t for t in tests if t.startswith(directory)]
             if not owned_tests:
                 continue
-            for owner in owners:
-                email_map[owner].append(directory)
+            email_map[tuple(owners)].append(directory)
         return email_map