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

Source/web/WebPluginScrollbarImpl.cpp

Index: Source/web/WebPluginScrollbarImpl.cpp
diff --git a/Source/web/WebPluginScrollbarImpl.cpp b/Source/web/WebPluginScrollbarImpl.cpp
index dd966494541437695ae5c0e196b4d8c49947f610..b7ffadc5f7638e463682a253e75cc7b5c24ece03 100644
--- a/Source/web/WebPluginScrollbarImpl.cpp
+++ b/Source/web/WebPluginScrollbarImpl.cpp
@@ -363,4 +363,14 @@ bool WebPluginScrollbarImpl::onKeyDown(const WebInputEvent& event)
     return false;
 }
 
+float WebPluginScrollbarImpl::elasticOverscroll() const
+{
+    return m_scrollbar->elasticOverscroll();
+}
+
+void WebPluginScrollbarImpl::setElasticOverscroll(float elasticOverscroll)
+{
+    m_scrollbar->setElasticOverscroll(elasticOverscroll);
+}
+
 } // namespace blink