Mac: Update scrollbar size and input position during impl-overscroll

Source/platform/exported/WebScrollbarImpl.cpp

Index: Source/platform/exported/WebScrollbarImpl.cpp
diff --git a/Source/platform/exported/WebScrollbarImpl.cpp b/Source/platform/exported/WebScrollbarImpl.cpp
index 57a20e4ba908a9c9d12324313839c40b0a07d6bc..c044b77ea19e1cd8a7c08ca09b30e5ab31581344 100644
--- a/Source/platform/exported/WebScrollbarImpl.cpp
+++ b/Source/platform/exported/WebScrollbarImpl.cpp
@@ -133,4 +133,14 @@ void WebScrollbarImpl::setIsAlphaLocked(bool flag)
     m_scrollbar->setIsAlphaLocked(flag);
 }
 
+float WebScrollbarImpl::elasticOverscroll() const
+{
+    return m_scrollbar->elasticOverscroll();
+}
+
+void WebScrollbarImpl::setElasticOverscroll(float elasticOverscroll)
+{
+    m_scrollbar->setElasticOverscroll(elasticOverscroll);
+}
+
 } // namespace blink