Assert that ComputedStyleBase is only templated with ComputedStyle

third_party/WebKit/Source/build/scripts/templates/ComputedStyleBase.h.tmpl

 {% from 'macros.tmpl' import license, print_if %}
 {% from 'fields/field.tmpl' import encode, getter_expression, setter_expression, declare_storage, fieldwise_compare, fieldwise_copy, fieldwise_diff, fieldwise_pointer_compare_inherited %}
 {% from 'fields/group.tmpl' import define_field_group_class %}
 {{license()}}
 
 #ifndef ComputedStyleBase_h
 #define ComputedStyleBase_h
 
 #include "core/style/ComputedStyleConstants.h"
 #include "core/CoreExport.h"
@@ skipping 148 matching lines @@
   {% endfor %}
 
  protected:
   // Constructor and destructor are protected so that only the parent class ComputedStyle
   // can instantiate this class.
   ALWAYS_INLINE ComputedStyleBase() :
   {% for field in computed_style.fields %}
       {{field.name}}({{encode(field, field.default_value)}}){{print_if(not loop.last, ',')}}
   {% endfor %}
   {
+    static_assert(std::is_same<ComputedStyle, ComputedStyleFinal>::value, "ComputedStyleBase can only be templated with ComputedStyle");

[alancutter (OOO until 2018), 2017/05/24 01:45:26]

Woah magic.

     {% for subgroup in computed_style.subgroups %}
     {{subgroup.member_name}}.Init();
     {% endfor %}
   }
 
   {% for field in computed_style.all_fields %}
   {% if field.field_template in ('storage_only', 'monotonic_flag', 'external') %}
   // {{field.property_name}}
   {{field_templates[field.field_template].decl_protected_methods(field)|indent(2)}}
 
@@ skipping 15 matching lines @@
 
  private:
   {% for field in computed_style.fields %}
   {{declare_storage(field)}}
   {% endfor %}
 };
 
 } // namespace blink
 
 #endif // ComputedStyleBase_h