IDL: Set dictionary default values in impl constructor

Source/bindings/templates/dictionary_impl.cpp

Index: Source/bindings/templates/dictionary_impl.cpp
diff --git a/Source/bindings/templates/dictionary_impl.cpp b/Source/bindings/templates/dictionary_impl.cpp
index 64fff01caf213821b850c615721a2350e08ee0ec..87152a4ba142fb21baf2539196dfb1099702b551 100644
--- a/Source/bindings/templates/dictionary_impl.cpp
+++ b/Source/bindings/templates/dictionary_impl.cpp
@@ -16,6 +16,9 @@ namespace blink {
 {# Constructor #}
 {{cpp_class}}::{{cpp_class}}()
 {
+    {% for member in members if member.cpp_default_value %}
+    {{member.setter_name}}({{member.cpp_default_value}});
+    {% endfor %}
 }
 
 void {{cpp_class}}::trace(Visitor* visitor)