Decouple Canvas from DisplayList and map Picture and PictureRecorder more directly to their Skia co…

sky/engine/bindings/scripts/templates/methods_cpp.template

 {##############################################################################}
 {# FIXME: We should return a rejected Promise if an error occurs in this
 function when ALL methods in this overload return Promise. In order to do so,
 we must ensure either ALL or NO methods in this overload return Promise #}
 {% macro overload_resolution_method(method) %}
 {% set overloads = method.overloads %}
 {% if method.is_static %}
   {% set offset = 0 %}
 {% else %}
   {% set offset = 1 %}
@@ skipping 317 matching lines @@
             exception = ToDart("Failed to fetch domWindow");
             goto fail;
         }
         Document& document = *domWindow->document();
 {% endif %}
         int argCount /* FIXME(vsm): Remove this. */ ALLOW_UNUSED = Dart_GetNativeArgumentCount(args);
 {% if constructor.has_exception_state %}
         ExceptionState es;
 {% endif %}
         {{generate_arguments(constructor) | indent(8)}}
+        {# TODO(iansf): The following line is incorrect if the constructor throws an exception.  In that case, we should not call AssociateWithDartWrapper, as the constructor may have returned a nullptr. #}
         {{constructor.cpp_value}}->AssociateWithDartWrapper(args);
 {% if constructor.has_exception_state %}
         if (es.had_exception()) {
+            {# TODO(iansf): The following line does not work in the case that an exception was thrown.  Investigate why. #}
             exception = es.GetDartException(args, {{constructor.auto_scope}});
             goto fail;
         }
 
 {% endif %}
         return;
     }
 
 {% if arguments_count > 0 or constructor.has_exception_state or is_constructor_call_with_execution_context or is_constructor_call_with_document or (constructor == named_constructor) %}
 fail:
@@ skipping 48 matching lines @@
 
 {##############################################################################}
 {% macro generate_symbolizer_constructor(dart_class, class_name, constructor) %}
 {% for native_entry in constructor.native_entries %}
 {% set resolver_string = native_entry.resolver_string %}
 if (native_function == {{dart_class}}Internal::{{static_method_name(constructor.name, constructor.overload_index)}}) {
   return reinterpret_cast<const uint8_t*>("{{resolver_string}}");
 }
 {% endfor %}
 {% endmacro %}