Add some missing includes

Change-Id: I720eb5226017bd588ba9dc441f8a34674a533285
diff --git a/dart_wrapper_info.h b/dart_wrapper_info.h
index 18844a2..d5b1f6f 100644
--- a/dart_wrapper_info.h
+++ b/dart_wrapper_info.h
@@ -5,6 +5,8 @@
 #ifndef LIB_TONIC_DART_WRAPPER_INFO_H_
 #define LIB_TONIC_DART_WRAPPER_INFO_H_
 
+#include <cstddef>
+
 namespace tonic {
 class DartWrappable;
 
diff --git a/scopes/dart_api_scope.h b/scopes/dart_api_scope.h
index 9d7a9ed..2edcf44 100644
--- a/scopes/dart_api_scope.h
+++ b/scopes/dart_api_scope.h
@@ -6,6 +6,7 @@
 #define LIB_TONIC_SCOPES_DART_API_SCOPE_H_
 
 #include "third_party/dart/runtime/include/dart_api.h"
+#include "tonic/common/macros.h"
 
 namespace tonic {