- Convert all isolate flags to a bit field.

runtime/bin/main.cc

Index: runtime/bin/main.cc
diff --git a/runtime/bin/main.cc b/runtime/bin/main.cc
index 9022af0d7ae16bc4e7dc11594b144129e5b74303..33e3bc1bebc765ca8017421b667bf59ba2372518 100644
--- a/runtime/bin/main.cc
+++ b/runtime/bin/main.cc
@@ -354,7 +354,6 @@ static bool ProcessFrontendOption(const char* filename,
     return false;
   }
   dfe.set_frontend_filename(filename);
-  vm_options->AddArgument("--use-dart-frontend");
   return true;
 }
 
@@ -1853,6 +1852,11 @@ void main(int argc, char** argv) {
   init_params.file_close = DartUtils::CloseFile;
   init_params.entropy_source = DartUtils::EntropySource;
   init_params.get_service_assets = GetVMServiceAssetsArchiveCallback;
+#if !defined(DART_PRECOMPILED_RUNTIME)
+  init_params.start_kernel_isolate = dfe.UseDartFrontend();
+#else
+  init_params.start_kernel_isolate = false;
+#endif
 
   char* error = Dart_Initialize(&init_params);
   if (error != NULL) {