Introduce LanguageMode, drop StrictMode.

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 103 matching lines @@
   // elements. This method should only be called for array expansion OR by
   // runtime JavaScript code that use InternalArrays and don't care about
   // EcmaScript 5.1 semantics.
   virtual void SetCapacityAndLength(
       Handle<JSArray> array,
       int capacity,
       int length) = 0;
 
   // Deletes an element in an object, returning a new elements backing store.
   MUST_USE_RESULT virtual MaybeHandle<Object> Delete(
-      Handle<JSObject> holder, uint32_t key, StrictMode strict_mode) = 0;
+      Handle<JSObject> holder, uint32_t key, LanguageMode language_mode) = 0;
 
   // If kCopyToEnd is specified as the copy_size to CopyElements, it copies all
   // of elements from source after source_start to the destination array.
   static const int kCopyToEnd = -1;
   // If kCopyToEndAndInitializeToHole is specified as the copy_size to
   // CopyElements, it copies all of elements from source after source_start to
   // destination array, padding any remaining uninitialized elements in the
   // destination array with the hole.
   static const int kCopyToEndAndInitializeToHole = -2;
 
@@ skipping 77 matching lines @@
 void CheckArrayAbuse(Handle<JSObject> obj, const char* op, uint32_t key,
                      bool allow_appending = false);
 
 MUST_USE_RESULT MaybeHandle<Object> ArrayConstructInitializeElements(
     Handle<JSArray> array,
     Arguments* args);
 
 } }  // namespace v8::internal
 
 #endif  // V8_ELEMENTS_H_