bindings: Make the sequence conversion code more complaint with WebIDL.

third_party/WebKit/Source/bindings/templates/union_container.cpp.tmpl

 {% from 'utilities.cpp.tmpl' import declare_enum_validation_variable %}
 {% from 'utilities.cpp.tmpl' import v8_value_to_local_cpp_value %}
 {#############################################################################}
 {% macro assign_and_return_if_hasinstance(member) %}
 {% if member.is_array_buffer_or_view_type %}
 if (v8Value->Is{{member.type_name}}()) {
 {% else %}
 if (V8{{member.type_name}}::hasInstance(v8Value, isolate)) {
 {% endif %}
   {{member.cpp_local_type}} cppValue = V8{{member.type_name}}::toImpl(v8::Local<v8::Object>::Cast(v8Value));
@@ skipping 81 matching lines @@
 
   {% endif %}
   {# 9., 10. ArrayBufferView #}
   {# FIXME: Individual typed arrays (e.g. Uint8Array) aren\'t supported yet. #}
   {% if array_buffer_view_type %}
   {{assign_and_return_if_hasinstance(array_buffer_view_type) | indent(2)}}
 
   {% endif %}
   {% if array_or_sequence_type %}
   {# 11.1, 11.2. Arrays and Sequences #}
-  {# FIXME: This should also check "object but not RegExp". Add checks
-     when we implement conversions for Date and RegExp. #}
-  {# TODO(bashi): Should check @@iterator symbol instead. #}
-  if (v8Value->IsArray()) {
+  if (IsV8Sequence(v8Value, isolate, exceptionState)) {
     {{v8_value_to_local_cpp_value(array_or_sequence_type) | indent}}
     impl.set{{array_or_sequence_type.type_name}}(cppValue);
     return;
   }
 
   {% endif %}
   {% if dictionary_type %}
   {# 11.3. Dictionaries #}
   if (v8Value->IsObject()) {
     {{v8_value_to_local_cpp_value(dictionary_type) | indent}}
@@ skipping 91 matching lines @@
 
 {{cpp_class}} NativeValueTraits<{{cpp_class}}>::NativeValue(v8::Isolate* isolate, v8::Local<v8::Value> value, ExceptionState& exceptionState) {
   {{cpp_class}} impl;
   {{v8_class}}::toImpl(isolate, value, impl, UnionTypeConversionMode::kNotNullable, exceptionState);
   return impl;
 }
 
 }  // namespace blink
 
 {% endfilter %}{# format_blink_cpp_source_code #}