Revert "Clean up the patch file for the isolate library by introducing a new builtin library: isola…

sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
index b982491d8218816a5622ca9fc2e7852ba4a5ac28..c342ff99bee1fa494330f2418d721e7919712b0b 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -1894,9 +1894,9 @@ $mainEnsureGetter
     if (compiler.isMockCompilation) return;
     Element main = compiler.mainApp.find(Compiler.MAIN);
     String mainCall = null;
-    if (compiler.isolateHelperLibrary != null) {
+    if (compiler.isolateLibrary != null) {
       Element isolateMain =
-        compiler.isolateHelperLibrary.find(Compiler.START_ROOT_ISOLATE);
+        compiler.isolateLibrary.find(Compiler.START_ROOT_ISOLATE);
       mainCall = buildIsolateSetup(buffer, main, isolateMain);
     } else {
       mainCall = '${namer.isolateAccess(main)}()';