Introduce LanguageMode, drop StrictMode.

src/runtime.js

 // Copyright 2006-2008 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.
 
 // This files contains runtime support implemented in JavaScript.
 
 // CAUTION: Some of the functions specified in this file are called
 // directly from compiled code. These are the functions with names in
 // ALL CAPS. The compiled code passes the first argument in 'this'.
 
@@ skipping 294 matching lines @@
 }
 
 
 
 /* -----------------------------
    - - -   H e l p e r s   - - -
    -----------------------------
 */
 
 // ECMA-262, section 11.4.1, page 46.
-function DELETE(key, strict) {
-  return %DeleteProperty(%ToObject(this), %ToName(key), strict);
+function DELETE(key, language_mode) {
+  return %DeleteProperty(%ToObject(this), %ToName(key), language_mode);
 }
 
 
 // ECMA-262, section 11.8.7, page 54.
 function IN(x) {
   if (!IS_SPEC_OBJECT(x)) {
     throw %MakeTypeError('invalid_in_operator_use', [this, x]);
   }
   if (%_IsNonNegativeSmi(this)) {
     if (IS_ARRAY(x) && %_HasFastPackedElements(x)) {
@@ skipping 360 matching lines @@
   return i;
 }
 
 
 // NOTE: Setting the prototype for Array must take place as early as
 // possible due to code generation for array literals.  When
 // generating code for a array literal a boilerplate array is created
 // that is cloned when running the code.  It is essential that the
 // boilerplate gets the right prototype.
 %FunctionSetPrototype($Array, new $Array(0));