bindings: Supports [Replaceable] accessors.

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 193 matching lines @@
 v8::Local<v8::Value> v8Value, const v8::FunctionCallbackInfo<v8::Value>& info
 {%- else %}
 v8::Local<v8::Value> v8Value, const v8::PropertyCallbackInfo<void>& info
 {%- endif %})
 {
     {% if attribute.is_reflect and attribute.idl_type == 'DOMString'
           and is_node and not attribute.is_implemented_in_private_script %}
     {% set cpp_class, v8_class = 'Element', 'V8Element' %}
     {% endif %}
     {# Local variables #}
-    {% if not attribute.is_static %}
+    {% if not attribute.is_static and not attribute.is_replaceable %}

[haraken, 2015/02/23 14:48:52]

For readability, it seems better to remove this branch. You can directly write
"v8::Local<v8::Object> holder = info.Holder()" just before where you actually
need the |holder|.

[Yuki, 2015/02/23 15:18:42]

Most of attributes need |holder|.  Only static attribute and replaceable
attribute do not need the holder.  Removing this branch makes things very
difficult, I think.

For example, line 218 and line 225, 243 use |holder|.  It's hard to write
"holder = info.Holder()" just before them without duplication.

     v8::Local<v8::Object> holder = info.Holder();
     {% endif %}
     {% if attribute.has_setter_exception_state %}
     ExceptionState exceptionState(ExceptionState::SetterContext, "{{attribute.name}}", "{{interface_name}}", holder, info.GetIsolate());
     {% endif %}
     {% if attribute.use_output_parameter_for_result %}
     {{attribute.cpp_type}} cppValue;
     {% endif %}
     {# impl #}
     {% if attribute.put_forwards %}
     {{cpp_class}}* proxyImpl = {{v8_class}}::toImpl(holder);
     {{attribute.cpp_type}} impl = WTF::getPtr(proxyImpl->{{attribute.name}}());
     if (!impl)
         return;
+    {% elif attribute.is_replaceable %}
+    {% if is_check_security %}

[haraken, 2015/02/23 14:48:52]

Why do we have the is_check_security clause only in the attribute.is_replaceable
clause? I guess the is_check_security clause would be needed in other clauses
(e.g., the attribute.put_forwards clause) as well.

[Yuki, 2015/02/23 15:18:42]

The code was copied from
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

I've not yet investigated about PutForwards.  I'll fix it if we need the check
for PutForwards, too, when I work on PutForwards.

However, PutForwards delegates the assignment to another attribute, so it's
possible that it's not the same as Replaceable.

+    {{cpp_class}}* impl = {{v8_class}}::toImpl(info.Holder());
+    ExceptionState exceptionState(ExceptionState::SetterContext, "{{attribute.name}}", "{{interface_name}}", info.Holder(), info.GetIsolate());
+    if (!BindingSecurity::shouldAllowAccessToFrame(info.GetIsolate(), impl->frame(), exceptionState)) {
+        exceptionState.throwIfNeeded();
+        return;
+    }
+    {% endif %}
+    if (info.This()->IsObject()) {
+        v8::Local<v8::String> propertyName = v8AtomicString(info.GetIsolate(), "{{attribute.name}}");
+        v8::Local<v8::Object>::Cast(info.This())->ForceSet(propertyName, v8Value);
+    }
     {% elif not attribute.is_static %}
     {{cpp_class}}* impl = {{v8_class}}::toImpl(holder);
     {% endif %}
     {% if attribute.idl_type == 'EventHandler' and interface_name == 'Window' %}
     if (!impl->document())
         return;
     {% endif %}
     {# Convert JS value to C++ value #}
     {% if attribute.idl_type != 'EventHandler' %}
+    {% if attribute.v8_value_to_local_cpp_value %}
     {{attribute.v8_value_to_local_cpp_value}};
+    {% endif %}
     {% elif not is_node %}{# EventHandler hack #}
     moveEventListenerToNewWrapper(info.GetIsolate(), holder, {{attribute.event_handler_getter_expression}}, v8Value, {{v8_class}}::eventListenerCacheIndex);
     {% endif %}
     {# Type checking, possibly throw a TypeError, per:
        http://www.w3.org/TR/WebIDL/#es-type-mapping #}
     {% if attribute.has_type_checking_interface %}
     {# Type checking for interface types (if interface not implemented, throw
        TypeError), per http://www.w3.org/TR/WebIDL/#es-interface #}
     if (!cppValue{% if attribute.is_nullable %} && !isUndefinedOrNull(v8Value){% endif %}) {
         exceptionState.throwTypeError("The provided value is not of type '{{attribute.idl_type}}'.");
@@ skipping 12 matching lines @@
           (attribute.is_reflect and
            not(attribute.idl_type == 'DOMString' and is_node)) %}
     {# Skip on compact node DOMString getters #}
     CustomElementProcessingStack::CallbackDeliveryScope deliveryScope;
     {% endif %}
     {% if attribute.is_call_with_execution_context or
           attribute.is_setter_call_with_execution_context %}
     ExecutionContext* executionContext = currentExecutionContext(info.GetIsolate());
     {% endif %}
     {# Set #}
+    {% if attribute.cpp_setter %}
     {{attribute.cpp_setter}};
+    {% endif %}
     {# Post-set #}
     {% if attribute.is_setter_raises_exception %}
     exceptionState.throwIfNeeded();
     {% endif %}
     {% if attribute.cached_attribute_validation_method %}
     V8HiddenValue::deleteHiddenValue(info.GetIsolate(), holder, v8AtomicString(info.GetIsolate(), "{{attribute.name}}")); // Invalidate the cached value.
     {% endif %}
 }
 {% endfilter %}
 {% endmacro %}
@@ skipping 141 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 %}