[bindings] add support for integer-indexed @@iterator

third_party/WebKit/Source/bindings/templates/interface_base.cpp

 {% include 'copyright_block.txt' %}
 #include "config.h"
 {% filter conditional(conditional_string) %}
 #include "{{v8_class_or_partial}}.h"
 
 {% for filename in cpp_includes if filename != '%s.h' % cpp_class_or_partial %}
 #include "{{filename}}"
 {% endfor %}
 
 namespace blink {
@@ skipping 328 matching lines @@
     ALLOW_UNUSED_LOCAL(instanceTemplate);
     v8::Local<v8::ObjectTemplate> prototypeTemplate = functionTemplate->PrototypeTemplate();
     ALLOW_UNUSED_LOCAL(prototypeTemplate);
     {% if custom_registration_methods %}
     ExecutionContext* context = currentExecutionContext(isolate);
     ALLOW_UNUSED_LOCAL(context);
     {% endif %}
     {% if has_access_check_callbacks %}
     instanceTemplate->SetAccessCheckCallbacks({{cpp_class}}V8Internal::namedSecurityCheck, {{cpp_class}}V8Internal::indexedSecurityCheck, v8::External::New(isolate, const_cast<WrapperTypeInfo*>(&{{v8_class}}::wrapperTypeInfo)));
     {% endif %}
+    {% if has_array_iterator %}
+    if (RuntimeEnabledFeatures::iterableCollectionsEnabled()) {

[Yuki, 2015/10/05 07:08:26]

Could you use {% filter runtime_enabled(...) %}?

+        prototypeTemplate->Set(v8::Symbol::GetIterator(isolate), v8::Array::GetValuesIterator(isolate), v8::DontEnum);

[caitp (gmail), 2015/10/04 23:10:47]

This doesn't use the V8DOMConfiguration helpers, because there isn't any
mechanism to set a symbol-keyed data property right now. It wouldn't be too much
work to add that, if that style is preferred?

Anyways, the gist of the functionality is here --- if the interface is found to
have an integer-typed "length" attribute, and a getter which takes a single
"unsigned long" argument, AND no other iterator type is declared, then the
default ArrayValues iterator from V8 is used.

The current version of this patch is blocked on
https://codereview.chromium.org/1378403004/ which exposes (all) of the builtin
Array iterator functions to the API. But, it could be rewritten to not need
that, and of course that CL can be shrunk a bit to not grow the native context
quite as much.

[Yuki, 2015/10/05 07:08:26]

Could you follow the way of the following?
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

Plus,
http://heycam.github.io/webidl/#es-iterators
says you need to define the iterator on the instance object, not on the
prototype object, in the case of [PrimaryGlobal] and [Global].  This applies to
Window interface.

I'm now introducing {{is_global}} in WIP CL http://crrev.com/1386843002 , but it
may take time.  Feel free to define your own {{is_global}}.
https://codereview.chromium.org/1386843002/diff/1/third_party/WebKit/Source/b...

[caitp (gmail), 2015/10/05 11:30:23]

I don't think there is any value in implementing the method in C++ in this case.
Maybe later on, once there is a way in C++ to construct a V8 Array Iterator. But
in this case, all that is needed is a non-enumerable symbol keyed data property,
which comes from V8.

So to do that, I'd have to change V8DOMConfiguration to add a method for adding
symbol-keyed data properties. I'm not sure how worthwhile that is. Is that what
you're asking for here?

On 2015/10/05 07:08:26, Yuki wrote:
That's a good point, done

+    }
+    {% endif %}
     {% for attribute in attributes
        if attribute.runtime_enabled_function and
           not attribute.exposed_test %}
     {% filter conditional(attribute.conditional_string) %}
     if ({{attribute.runtime_enabled_function}}()) {
         {% if attribute.is_data_type_property %}
         const V8DOMConfiguration::AttributeConfiguration attributeConfiguration = \
         {{attribute_configuration(attribute)}};
         V8DOMConfiguration::installAttribute(isolate, instanceTemplate, prototypeTemplate, attributeConfiguration);
         {% else %}
@@ skipping 136 matching lines @@
 {% endfor %}
 {% for attribute in attributes if attribute.is_implemented_in_private_script %}
 {{attribute_getter_implemented_in_private_script(attribute)}}
 {% if attribute.has_setter %}
 {{attribute_setter_implemented_in_private_script(attribute)}}
 {% endif %}
 {% endfor %}
 {% block partial_interface %}{% endblock %}
 } // namespace blink
 {% endfilter %}