VM: Allow configuring use_field_guards on the per-isolate basis and include it into snapshot featur…

runtime/vm/kernel_isolate.cc

Index: runtime/vm/kernel_isolate.cc
diff --git a/runtime/vm/kernel_isolate.cc b/runtime/vm/kernel_isolate.cc
index f14b99eccd0ef9c286f9ed8924c8b7bef96c454d..03b6565aeae5c0c2f09c87edc797074e212c3620 100644
--- a/runtime/vm/kernel_isolate.cc
+++ b/runtime/vm/kernel_isolate.cc
@@ -68,12 +68,15 @@ class RunKernelTask : public ThreadPool::Task {
       return;
     }
 
+    // Note: these flags must match those passed to the VM during
+    // the app-jit training run (see //utils/kernel-service/BUILD.gn).
     Dart_IsolateFlags api_flags;
     api_flags.version = DART_FLAGS_CURRENT_VERSION;
     api_flags.enable_type_checks = false;
     api_flags.enable_asserts = false;
     api_flags.enable_error_on_bad_type = false;
     api_flags.enable_error_on_bad_override = false;
+    api_flags.use_field_guards = true;
 
     isolate = reinterpret_cast<Isolate*>(create_callback(
         KernelIsolate::kName, NULL, NULL, NULL, &api_flags, NULL, &error));