Support web workers in dart2js.

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

Index: sdk/lib/_internal/compiler/implementation/lib/foreign_helper.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/lib/foreign_helper.dart	(revision 16024)
+++ sdk/lib/_internal/compiler/implementation/lib/foreign_helper.dart	(working copy)
@@ -13,12 +13,12 @@
 dynamic UNINTERCEPTED(var expression) {}
 
 /**
- * Returns [:true:] if [object] has its own operator== definition.
+ * Return [:true:] if [object] has its own operator== definition.
  */
 bool JS_HAS_EQUALS(var object) {}
 
 /**
- * Returns the isolate in which this code is running.
+ * Return the isolate in which this code is running.
  */
 dynamic JS_CURRENT_ISOLATE() {}
 
@@ -28,6 +28,16 @@
 dynamic JS_CALL_IN_ISOLATE(var isolate, Function function) {}
 
 /**
- * Convers the Dart closure [function] into a JavaScript closure.
+ * Convert the Dart closure [function] into a JavaScript closure.
  */
 dynamic DART_CLOSURE_TO_JS(Function function) {}
+
+/**
+ * Set the current isolate to [isolate].
+ */
+void JS_SET_CURRENT_ISOLATE(var isolate) {}
+
+/**
+ * Create an isolate and return it.
+ */
+dynamic JS_CREATE_ISOLATE() {}