[runtime] Avoid @@isConcatSpreadable lookup for fast path Array.prototype.concat

test/cctest/heap/test-heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1674 matching lines @@
   CompileRun(source.start());
 }
 
 
 // Count the number of native contexts in the weak list of native contexts.
 int CountNativeContexts() {
   int count = 0;
   Object* object = CcTest::heap()->native_contexts_list();
   while (!object->IsUndefined()) {
     count++;
-    object = Context::cast(object)->get(Context::NEXT_CONTEXT_LINK);
+    object = Context::cast(object)->next_context_link();
   }
   return count;
 }
 
 
 // Count the number of user functions in the weak list of optimized
 // functions attached to a native context.
 static int CountOptimizedUserFunctions(v8::Local<v8::Context> context) {
   int count = 0;
   Handle<Context> icontext = v8::Utils::OpenHandle(*context);
@@ skipping 117 matching lines @@
 // Count the number of native contexts in the weak list of native contexts
 // causing a GC after the specified number of elements.
 static int CountNativeContextsWithGC(Isolate* isolate, int n) {
   Heap* heap = isolate->heap();
   int count = 0;
   Handle<Object> object(heap->native_contexts_list(), isolate);
   while (!object->IsUndefined()) {
     count++;
     if (count == n) heap->CollectAllGarbage();
     object =
-        Handle<Object>(Context::cast(*object)->get(Context::NEXT_CONTEXT_LINK),
-                       isolate);
+        Handle<Object>(Context::cast(*object)->next_context_link(), isolate);
   }
   return count;
 }
 
 
 // Count the number of user functions in the weak list of optimized
 // functions attached to a native context causing a GC after the
 // specified number of elements.
 static int CountOptimizedUserFunctionsWithGC(v8::Local<v8::Context> context,
                                              int n) {
@@ skipping 4762 matching lines @@
       heap->RightTrimFixedArray<Heap::CONCURRENT_TO_SWEEPER>(arrays[j], N - 1);
     }
   }
   // Force allocation from the free list.
   heap->set_force_oom(true);
   heap->CollectGarbage(OLD_SPACE);
 }
 
 }  // namespace internal
 }  // namespace v8