[CSS Regions] Add new regionOversetChange event

Source/core/dom/ElementRareData.cpp

Index: Source/core/dom/ElementRareData.cpp
diff --git a/Source/core/dom/ElementRareData.cpp b/Source/core/dom/ElementRareData.cpp
index 24e14a9d857839f529448010ae902949348f1aec..dd404bf8a7038b1b6eabdff9151f94fef9456201 100644
--- a/Source/core/dom/ElementRareData.cpp
+++ b/Source/core/dom/ElementRareData.cpp
@@ -32,6 +32,7 @@
 #include "core/dom/ElementRareData.h"
 
 #include "core/dom/WebCoreMemoryInstrumentation.h"
+#include "core/rendering/RegionOversetState.h"
 #include "core/rendering/style/RenderStyle.h"
 
 namespace WebCore {
@@ -39,6 +40,7 @@ namespace WebCore {
 struct SameSizeAsElementRareData : NodeRareData {
     short indices[2];
     unsigned bitfields;
+    RegionOversetState regionOversetState;
     LayoutSize sizeForResizing;
     IntSize scrollOffset;
     void* pointers[9];