Support spawnUri in app snapshots.

runtime/lib/isolate.cc

Index: runtime/lib/isolate.cc
diff --git a/runtime/lib/isolate.cc b/runtime/lib/isolate.cc
index 4eff30795a604e3d295aebcad0fc1e90b57a8fce..337fec151f855859e5fd4a2197e43a868a337abf 100644
--- a/runtime/lib/isolate.cc
+++ b/runtime/lib/isolate.cc
@@ -340,10 +340,11 @@ DEFINE_NATIVE_ENTRY(Isolate_spawnUri, 12) {
   GET_NATIVE_ARGUMENT(String, packageRoot, arguments->NativeArgAt(10));
   GET_NATIVE_ARGUMENT(String, packageConfig, arguments->NativeArgAt(11));
 
-  if (Snapshot::IncludesCode(Dart::snapshot_kind())) {
+  if (Dart::snapshot_kind() == Snapshot::kAppAOT) {
     const Array& args = Array::Handle(Array::New(1));
-    args.SetAt(0, String::Handle(String::New(
-                      "Isolate.spawnUri not supported under precompilation")));
+    args.SetAt(
+        0, String::Handle(String::New(
+               "Isolate.spawnUri not supported when using AOT compilation")));
     Exceptions::ThrowByType(Exceptions::kUnsupported, args);
     UNREACHABLE();
   }