Bug 1620035 - Convert GenerateFrameLists.py to py3; r=firefox-build-system-reviewers,rstewart

Depends on D65377

Differential Revision: https://phabricator.services.mozilla.com/D65378

--HG--
extra : moz-landing-system : lando

layout/generic/GenerateFrameLists.py

@@ -17,8 +17,7 @@ def grouped_frame_classes():
         if frame.is_concrete:
             groups.setdefault(frame.ty, []).append(frame)
     groups = groups.values()
-    groups.sort(key=lambda x: (-len(x), x[0].ty if len(x) > 1 else x[0].cls))
-    return groups
+    return sorted(groups, key=lambda x: (-len(x), x[0].ty if len(x) > 1 else x[0].cls))
 
 
 def generate_frame_id_list_h(output, *ignore):

layout/generic/moz.build

@@ -235,11 +235,9 @@ SOURCES += [
 
 GeneratedFile('FrameIdList.h',
               script='GenerateFrameLists.py',
-              py2=True,
               entry_point='generate_frame_id_list_h')
 GeneratedFile('FrameTypeList.h',
               script='GenerateFrameLists.py',
-              py2=True,
               entry_point='generate_frame_type_list_h')
 
 include('/ipc/chromium/chromium-config.mozbuild')