Clean up ComputedStyle field templates.

third_party/WebKit/Source/build/scripts/templates/fields/monotonic_flag.tmpl

-{% from 'fields/field.tmpl' import encode, argument_type %}
+{% import 'fields/base.tmpl' as base %}
+{% from 'fields/field.tmpl' import encode %}
+
 {% macro decl_public_methods(field) %}
-bool {{field.getter_method_name}}() const {
-  return {{field.name}};
-}
+{{base.decl_getter_method(field)}}
 void {{field.setter_method_name}}() {
   {{field.name}} = {{encode(field, "true")}};
 }
 {% endmacro %}
+
 {% macro decl_protected_methods(field) -%}
-void {{field.internal_setter_method_name}}({{argument_type(field)}} v) {
-  {{field.name}} = {{encode(field, "v")}};
-}
+{{base.decl_internal_setter_method(field)}}
 {%- endmacro %}