Filter out shorthands for make_computed_style_base.py.

third_party/WebKit/Source/build/scripts/make_computed_style_base.py

Index: third_party/WebKit/Source/build/scripts/make_computed_style_base.py
diff --git a/third_party/WebKit/Source/build/scripts/make_computed_style_base.py b/third_party/WebKit/Source/build/scripts/make_computed_style_base.py
index e2849de568032b787c69592f3b46b8e5e232ae6c..be2f62897f2d30a6f7d987d4198d41ce5feacb5b 100755
--- a/third_party/WebKit/Source/build/scripts/make_computed_style_base.py
+++ b/third_party/WebKit/Source/build/scripts/make_computed_style_base.py
@@ -317,7 +317,13 @@ class ComputedStyleBaseWriter(make_style_builder.StyleBuilderWriter):
             if 'type_name' not in property_:
                 property_['type_name'] = 'E' + enum_type_name(property_['name_for_methods'])
 
-        property_values = self._properties.values()
+        # Ignore shorthand properties
+        for property_ in self._properties.values():
+            if property_['field_template'] is not None:
+                assert not property_['longhands'], \
+                    "Shorthand '{}' cannot have a field_template.".format(property_['name'])
+
+        property_values = [value for value in self._properties.values() if not value['longhands']]
 
         for property_ in property_values:
             # Override the type name when field_type_path is specified