Array.prototype.unshift builtin improvements

src/elements.h

 // 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.
 
 #ifndef V8_ELEMENTS_H_
 #define V8_ELEMENTS_H_
 
 #include "src/elements-kind.h"
 #include "src/heap/heap.h"
 #include "src/isolate.h"
@@ skipping 107 matching lines @@
 
   virtual void Reconfigure(Handle<JSObject> object,
                            Handle<FixedArrayBase> backing_store, uint32_t entry,
                            Handle<Object> value,
                            PropertyAttributes attributes) = 0;
 
   virtual void Add(Handle<JSObject> object, uint32_t index,
                    Handle<Object> value, PropertyAttributes attributes,
                    uint32_t new_capacity) = 0;
 
+  virtual uint32_t Unshift(Handle<JSArray> receiver,
+                           Handle<FixedArrayBase> backing_store, Arguments args,
+                           uint32_t add_count) = 0;
+
   // TODO(cbruni): Consider passing Arguments* instead of Object** depending on
   // the requirements of future callers.
   virtual uint32_t Push(Handle<JSArray> receiver,
                         Handle<FixedArrayBase> backing_store, Object** objects,
                         uint32_t start, int direction) = 0;
 
   virtual Handle<JSArray> Splice(Handle<JSArray> receiver,
                                  Handle<FixedArrayBase> backing_store,
                                  uint32_t start, uint32_t delete_count,
                                  Arguments args, uint32_t add_count) = 0;
@@ skipping 30 matching lines @@
 void CheckArrayAbuse(Handle<JSObject> obj, const char* op, uint32_t index,
                      bool allow_appending = false);
 
 MUST_USE_RESULT MaybeHandle<Object> ArrayConstructInitializeElements(
     Handle<JSArray> array,
     Arguments* args);
 
 } }  // namespace v8::internal
 
 #endif  // V8_ELEMENTS_H_