Speed up fremontcut/dartdomgenerator

lib/html/scripts/systembase.py

Index: lib/html/scripts/systembase.py
diff --git a/lib/html/scripts/systembase.py b/lib/html/scripts/systembase.py
index 1e1f9491cdb82fc02080feebce7f32a706ee118b..f7cbef9d43b03f5371297c8930eed36392752171 100644
--- a/lib/html/scripts/systembase.py
+++ b/lib/html/scripts/systembase.py
@@ -72,7 +72,7 @@ class BaseGenerator(object):
     for const in sorted(interface.constants, ConstantOutputOrder):
       self.AddConstant(const)
 
-    for attr in interface.attributes:
+    for attr in sorted(interface.attributes, ConstantOutputOrder):
       if attr.type.id != 'EventListener':
         self.AddAttribute(attr)
 
@@ -107,7 +107,7 @@ class BaseGenerator(object):
     for parent_interface in secondary_parents:
       if isinstance(parent_interface, str):  # IsDartCollectionType(parent_interface)
         continue
-      for attr in parent_interface.attributes:
+      for attr in sorted(parent_interface.attributes, ConstantOutputOrder):
         if not FindMatchingAttribute(interface, attr):
           self.AddSecondaryAttribute(parent_interface, attr)