IDL: Remove support for [LogPreviousValue] extended attribute

Source/bindings/templates/attributes.cpp

 {##############################################################################}
 {% macro attribute_getter(attribute, world_suffix) %}
 {% filter conditional(attribute.conditional_string) %}
 static void {{attribute.name}}AttributeGetter{{world_suffix}}(
 {%- if attribute.is_expose_js_accessors %}
 const v8::FunctionCallbackInfo<v8::Value>& info
 {%- else %}
 const v8::PropertyCallbackInfo<v8::Value>& info
 {%- endif %})
 {
@@ skipping 295 matching lines @@
     UseCounter::count(callingExecutionContext(info.GetIsolate()), UseCounter::{{attribute.measure_as}});
     {% endif %}
     {% if world_suffix in attribute.activity_logging_world_list_for_setter %}
     ScriptState* scriptState = ScriptState::from(info.GetIsolate()->GetCurrentContext());
     V8PerContextData* contextData = scriptState->perContextData();
     {% if attribute.activity_logging_world_check %}
     if (scriptState->world().isIsolatedWorld() && contextData && contextData->activityLogger()) {
     {% else %}
     if (contextData && contextData->activityLogger()) {
     {% endif %}
-        {% if attribute.activity_logging_include_old_value_for_setter %}
-        {{cpp_class}}* impl = {{v8_class}}::toImpl(info.Holder());
-        {% if attribute.cpp_value_original %}
-        {{attribute.cpp_type}} {{attribute.cpp_value}}({{attribute.cpp_value_original}});
-        {% endif %}
-        v8::Handle<v8::Value> originalValue = {{attribute.cpp_value_to_v8_value}};
-        contextData->activityLogger()->logSetter("{{interface_name}}.{{attribute.name}}", v8Value, originalValue);
-        {% else %}
         contextData->activityLogger()->logSetter("{{interface_name}}.{{attribute.name}}", v8Value);
-        {% endif %}
     }
     {% endif %}
     {% if attribute.is_custom_element_callbacks or attribute.is_reflect %}
     CustomElementProcessingStack::CallbackDeliveryScope deliveryScope;
     {% endif %}
     {% if attribute.has_custom_setter %}
     {{v8_class}}::{{attribute.name}}AttributeSetterCustom(v8Value, info);
     {% else %}
     {{cpp_class}}V8Internal::{{attribute.name}}AttributeSetter{{world_suffix}}(v8Value, info);
     {% endif %}
@@ skipping 109 matching lines @@
        access_control,
        property_attribute,
        only_exposed_to_private_script,
    ] %}
 {% if not attribute.is_expose_js_accessors %}
 {% set attribute_configuration_list = attribute_configuration_list
                                     + [on_prototype] %}
 {% endif %}
 {{'{'}}{{attribute_configuration_list | join(', ')}}{{'}'}}
 {%- endmacro %}