Log to UMA when x-origin frames (1) are created and (2) become visible

third_party/WebKit/Source/core/dom/Document.h

Index: third_party/WebKit/Source/core/dom/Document.h
diff --git a/third_party/WebKit/Source/core/dom/Document.h b/third_party/WebKit/Source/core/dom/Document.h
index d641d2076d6b54f2eca18e4a68df8338b47f539b..a9346ea2511fe761f87b9ad3155eb4f281bcd6f3 100644
--- a/third_party/WebKit/Source/core/dom/Document.h
+++ b/third_party/WebKit/Source/core/dom/Document.h
@@ -1094,6 +1094,8 @@ public:
 
     bool isInMainFrame() const;
 
+    void onVisibilityMaybeChanged(bool visible);
+
 protected:
     Document(const DocumentInit&, DocumentClassFlags = DefaultDocumentClass);
 
@@ -1416,6 +1418,8 @@ private:
     bool m_mayContainV0Shadow = false;
 
     Member<SnapCoordinator> m_snapCoordinator;
+
+    bool m_visibilityWasLogged;
 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT Supplement<Document>;