[proxies] Make Array.isArray respect proxies.

src/builtins.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/builtins.h"
 
 #include "src/api.h"
 #include "src/api-natives.h"
 #include "src/arguments.h"
 #include "src/base/once.h"
@@ skipping 1405 matching lines @@
 
   Handle<JSArray> result_array;
   if (Fast_ArrayConcat(isolate, &args).ToHandle(&result_array)) {
     return *result_array;
   }
   if (isolate->has_pending_exception()) return isolate->heap()->exception();
   return Slow_ArrayConcat(&args, isolate);
 }
 
 
+// ES6 section 22.1.2.2 Array.isArray
+BUILTIN(ArrayIsArray) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(2, args.length());
+  Handle<Object> object = args.at<Object>(1);
+  Maybe<bool> result = Object::IsArray(object);
+  MAYBE_RETURN(result, isolate->heap()->exception());
+  return *isolate->factory()->ToBoolean(result.FromJust());
+}
+
+
 // ES6 section 26.1.3 Reflect.defineProperty
 BUILTIN(ReflectDefineProperty) {
   HandleScope scope(isolate);
   DCHECK_EQ(4, args.length());
   Handle<Object> target = args.at<Object>(1);
   Handle<Object> key = args.at<Object>(2);
   Handle<Object> attributes = args.at<Object>(3);
 
   if (!target->IsJSReceiver()) {
     THROW_NEW_ERROR_RETURN_FAILURE(
@@ skipping 995 matching lines @@
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 }  // namespace internal
 }  // namespace v8