Split Size into Size and Offset.

sky/engine/core/script/dom_dart_state.h

Index: sky/engine/core/script/dom_dart_state.h
diff --git a/sky/engine/core/script/dom_dart_state.h b/sky/engine/core/script/dom_dart_state.h
index ba45f36bafd88ba09cb110a232cfc2499e2da294..3aaf9a797a26acd3106659093ef310f1e3e3f7eb 100644
--- a/sky/engine/core/script/dom_dart_state.h
+++ b/sky/engine/core/script/dom_dart_state.h
@@ -34,6 +34,8 @@ class DOMDartState : public DartState {
   // Cached handles to strings used in Dart/C++ conversions.
   Dart_Handle x_handle() { return x_handle_.value(); }
   Dart_Handle y_handle() { return y_handle_.value(); }
+  Dart_Handle dx_handle() { return dx_handle_.value(); }
+  Dart_Handle dy_handle() { return dy_handle_.value(); }
   Dart_Handle value_handle() { return value_handle_.value(); }
   Dart_Handle color_class() { return color_class_.value(); }
 
@@ -43,6 +45,8 @@ class DOMDartState : public DartState {
 
   DartPersistentValue x_handle_;
   DartPersistentValue y_handle_;
+  DartPersistentValue dx_handle_;
+  DartPersistentValue dy_handle_;
   DartPersistentValue value_handle_;
   DartPersistentValue color_class_;
 };