Add !IsArray() check for dictionary conversion in union types

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

 {% from 'utilities.cpp' import declare_enum_validation_variable %}
 {% include 'copyright_block.txt' %}
 #include "{{this_include_header_name}}.h"
 
 {% from 'utilities.cpp' import v8_value_to_local_cpp_value %}
 {% macro assign_and_return_if_hasinstance(member) %}
 if (V8{{member.type_name}}::hasInstance(v8Value, isolate)) {
     {{member.cpp_local_type}} cppValue = V8{{member.type_name}}::toImpl(v8::Local<v8::Object>::Cast(v8Value));
     impl.set{{member.type_name}}(cppValue);
     return;
@@ skipping 75 matching lines @@
     {# 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}}
 
     {% endif %}
     {% if dictionary_type %}
     {# 12. Dictionaries #}
     {# FIXME: This should also check "object but not Date or RegExp". Add checks
        when we implement conversions for Date and RegExp. #}
-    if (isUndefinedOrNull(v8Value) || v8Value->IsObject()) {
+    {# TODO(bashi): The spec doesn't say we should check !IsArray() but otherwise
+       we can't distinguish a sequence<T> and a dictionary.
+       https://github.com/heycam/webidl/issues/123 #}
+    if (isUndefinedOrNull(v8Value) || (v8Value->IsObject() && !v8Value->IsArray())) {
         {{v8_value_to_local_cpp_value(dictionary_type) | indent(8)}}
         impl.set{{dictionary_type.type_name}}(cppValue);
         return;
     }
 
     {% endif %}
     {% if array_or_sequence_type %}
     {# 13.1, 13.2. Arrays and Sequences #}
     {# FIXME: This should also check "object but not Date or RegExp". Add checks
        when we implement conversions for Date and RegExp. #}
@@ skipping 85 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::NotNullable, exceptionState);
     return impl;
 }
 
 } // namespace blink