dart2js: make "CREATE_JS_ISOLATE" an embedded global.

pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart

Index: pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart b/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
index 25d4b43ff58ea22c11de73b98afa48a160209267..c15f2ed97058e1a61077891f4364439c9f7072f5 100644
--- a/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
@@ -366,6 +366,12 @@ class OldEmitter implements Emitter {
     }
 
     if (hasIsolateSupport) {
+      jsAst.Expression createNewIsolateFunctionAccess =
+          generateEmbeddedGlobalAccess(embeddedNames.CREATE_NEW_ISOLATE);
+      var createIsolateAssignment =
+          js('# = function() { return new ${namer.isolateName}(); }',
+             createNewIsolateFunctionAccess);
+
       jsAst.Expression classIdExtractorAccess =
           generateEmbeddedGlobalAccess(embeddedNames.CLASS_ID_EXTRACTOR);
       var classIdExtractorAssignment =
@@ -402,7 +408,8 @@ class OldEmitter implements Emitter {
         return o;
       }''', [ initializeEmptyInstanceAccess, allClassesAccess ]);
 
-      result.addAll([classIdExtractorAssignment,
+      result.addAll([createIsolateAssignment,
+                     classIdExtractorAssignment,
                      classFieldsExtractorAssignment,
                      instanceFromClassIdAssignment,
                      initializeEmptyInstanceAssignment]);