Initialize the global dart library natives separately and outside the isolate create callback

sky/engine/bindings/dart_ui.cc

@@ -42,7 +42,7 @@ const uint8_t* GetSymbol(Dart_NativeFunction native_function) {
 
 }  // namespace
 
-void DartUI::InitForIsolate() {
+void DartUI::InitForGlobal() {
   if (!g_natives) {
     g_natives = new DartLibraryNatives();
     Canvas::RegisterNatives(g_natives);
@@ -64,7 +64,10 @@ void DartUI::InitForIsolate() {
     SceneBuilder::RegisterNatives(g_natives);
     Window::RegisterNatives(g_natives);
   }
+}
 
+void DartUI::InitForIsolate() {
+  DCHECK(g_natives);
   DART_CHECK_VALID(Dart_SetNativeResolver(
       Dart_LookupLibrary(ToDart("dart:ui")), GetNativeFunction, GetSymbol));
 }

sky/engine/bindings/dart_ui.h

@@ -11,6 +11,7 @@ namespace blink {
 
 class DartUI {
  public:
+  static void InitForGlobal();
   static void InitForIsolate();
 
  private:

sky/engine/core/script/dart_init.cc

@@ -290,6 +290,8 @@ void InitDartVM() {
     DartDebugger::InitDebugger();
   }
 
+  DartUI::InitForGlobal();
+
   {
     TRACE_EVENT0("flutter", "Dart_Initialize");
     CHECK(Dart_Initialize(reinterpret_cast<uint8_t*>(