[Bindings] Replace void cast with ALLOW_UNUSED_LOCAL in dictionary_v8.cpp.tmpl.

third_party/WebKit/Source/bindings/templates/dictionary_v8.cpp.tmpl

 {% filter format_blink_cpp_source_code %}
 
 {% from 'utilities.cpp.tmpl' import declare_enum_validation_variable %}
 {% include 'copyright_block.txt' %}
 #include "{{v8_original_class}}.h"
 
 {% for filename in cpp_includes if filename != '%s.h' % v8_class %}
 #include "{{filename}}"
 {% endfor %}
 
@@ skipping 10 matching lines @@
   if (!v8Value->IsObject()) {
     {% if use_permissive_dictionary_conversion %}
     // Do nothing.
     return;
     {% else %}
     exceptionState.throwTypeError("cannot convert to dictionary.");
     return;
     {% endif %}
   }
   v8::Local<v8::Object> v8Object = v8Value.As<v8::Object>();
-  (void)v8Object;
+  ALLOW_UNUSED_LOCAL(v8Object);
 
   {% if parent_v8_class %}
   {{parent_v8_class}}::toImpl(isolate, v8Value, impl, exceptionState);
   if (exceptionState.hadException())
     return;
 
   {% endif %}
   {# Declare local variables only when the dictionary has members to avoid unused variable warnings. #}
   {% if members %}
   v8::TryCatch block(isolate);
@@ skipping 84 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, exceptionState);
   return impl;
 }
 
 }  // namespace blink
 
 {% endfilter %}{# format_blink_cpp_source_code #}