dart2js: make "CREATE_JS_ISOLATE" an embedded global.

sdk/lib/_internal/compiler/js_lib/foreign_helper.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library _foreign_helper;
 
 /**
  * Emits a JavaScript code fragment parameterized by arguments.
  *
  * Hash characters `#` in the [codeTemplate] are replaced in left-to-right order
@@ skipping 136 matching lines @@
  * https://code.google.com/p/v8/wiki/JavaScriptStackTraceApi.
  */
 RAW_DART_FUNCTION_REF(Function function) {}
 
 /**
  * Sets the current isolate to [isolate].
  */
 void JS_SET_CURRENT_ISOLATE(isolate) {}
 
 /**
- * Creates an isolate and returns it.
- */
-JS_CREATE_ISOLATE() {}
-
-/**
  * Returns the JavaScript constructor function for Dart's Object class.
  * This can be used for type tests, as in
  *
  *     if (JS('bool', '# instanceof #', obj, JS_DART_OBJECT_CONSTRUCTOR()))
  *       ...
  */
 JS_DART_OBJECT_CONSTRUCTOR() {}
 
 /**
  * Returns the interceptor for class [type].  The interceptor is the type's
@@ skipping 115 matching lines @@
 }
 
 /**
  * JavaScript string concatenation. Inputs must be Strings.  Corresponds to the
  * HStringConcat SSA instruction and may be constant-folded.
  */
 String JS_STRING_CONCAT(String a, String b) {
   // This body is unused, only here for type analysis.
   return JS('String', '# + #', a, b);
 }