Fix a use of native JS code to avoid substituting lvalues with '#'.

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

Index: sdk/lib/_internal/compiler/implementation/lib/isolate_patch.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/isolate_patch.dart b/sdk/lib/_internal/compiler/implementation/lib/isolate_patch.dart
index 0711b7d790a648f5ef84e533ca4339127e5a6fb5..c6356bfb9fc3c830b4d073a33170399371f7bc3a 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/isolate_patch.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/isolate_patch.dart
@@ -188,9 +188,9 @@ class _Manager {
   }
 
   void _nativeDetectEnvironment() {
-    JS("void", r"#.isWorker = $isWorker", this);
-    JS("void", r"#.supportsWorkers = $supportsWorkers", this);
-    JS("void", r"#.fromCommandLine = typeof(window) == 'undefined'", this);
+    isWorker = JS("bool", r"$isWorker");
+    supportsWorkers = JS("bool", r"$supportsWorkers");
+    fromCommandLine = JS("bool", r"typeof(window) == 'undefined'");
   }
 
   void _nativeInitWorkerMessageHandler() {