VM: Make use_osr an Isolate flag, similar to how we made use_field_guards.

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 d0a09f80faa1d4cff8dcc778103244c473c21211..0b6e86761c4b5443584dfe9b8adb89e6a5b8d469 100644
--- a/runtime/vm/kernel_isolate.cc
+++ b/runtime/vm/kernel_isolate.cc
@@ -71,15 +71,14 @@ class RunKernelTask : public ThreadPool::Task {
     // 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;
+    Isolate::FlagsInitialize(&api_flags);
     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;
-#if defined(DART_PRECOMPILER)
-    api_flags.use_field_guards = false;
-#else
+#if !defined(DART_PRECOMPILER)
     api_flags.use_field_guards = true;
+    api_flags.use_osr = true;
 #endif
 
     isolate = reinterpret_cast<Isolate*>(create_callback(