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

Source/platform/exported/WebScrollbarThemeClientImpl.cpp

Index: Source/platform/exported/WebScrollbarThemeClientImpl.cpp
diff --git a/Source/platform/exported/WebScrollbarThemeClientImpl.cpp b/Source/platform/exported/WebScrollbarThemeClientImpl.cpp
index 9343d0086ac87b4684751573277c612b48fa4d7a..801f7db29d10bfe4111ca2fa982a6aed2e9978d0 100644
--- a/Source/platform/exported/WebScrollbarThemeClientImpl.cpp
+++ b/Source/platform/exported/WebScrollbarThemeClientImpl.cpp
@@ -220,4 +220,14 @@ void WebScrollbarThemeClientImpl::setIsAlphaLocked(bool flag)
     m_scrollbar->setIsAlphaLocked(flag);
 }
 
+float WebScrollbarThemeClientImpl::elasticOverscroll() const
+{
+    return m_scrollbar->elasticOverscroll();
+}
+
+void WebScrollbarThemeClientImpl::setElasticOverscroll(float elasticOverscroll)
+{
+    return m_scrollbar->setElasticOverscroll(elasticOverscroll);
+}
+
 } // namespace blink