Add the c++ code part of bindings2/

sky/engine/tonic/dart_builtin.cc

Index: sky/engine/tonic/dart_builtin.cc
diff --git a/sky/engine/tonic/dart_builtin.cc b/sky/engine/tonic/dart_builtin.cc
index 9a8f5356ab724f8bdbae0ee2c192d49e5c8449c3..aa12de497f3f5a397bf2ac1d47ce9c1375cbed9c 100644
--- a/sky/engine/tonic/dart_builtin.cc
+++ b/sky/engine/tonic/dart_builtin.cc
@@ -9,6 +9,7 @@
 #include <string.h>
 
 #include "base/logging.h"
+#include "sky/engine/tonic/dart_converter.h"
 
 namespace blink {
 
@@ -47,4 +48,10 @@ const uint8_t* DartBuiltin::Symbolizer(Dart_NativeFunction native_function) cons
   return nullptr;
 }
 
+Dart_Handle DartBuiltin::LookupLibrary(const char* name) {
+    Dart_Handle library = Dart_LookupLibrary(ToDart(name));
+    DCHECK(!Dart_IsError(library));
+    return library;
+}
+
 }  // namespace blink