Fix smooth scroll jump when switching scroll handling between MT and CC

cc/blink/web_layer_impl.cc

Index: cc/blink/web_layer_impl.cc
diff --git a/cc/blink/web_layer_impl.cc b/cc/blink/web_layer_impl.cc
index 56e1d0cf2f8b298b74bc3d58a3e327a226e7b8e8..5ff3e47fa9675fea63f7918f2d700df64f263b2a 100644
--- a/cc/blink/web_layer_impl.cc
+++ b/cc/blink/web_layer_impl.cc
@@ -330,8 +330,14 @@ void WebLayerImpl::addMainThreadScrollingReasons(
   layer_->AddMainThreadScrollingReasons(main_thread_scrolling_reasons);
 }
 
-void WebLayerImpl::clearMainThreadScrollingReasons() {
-  layer_->ClearMainThreadScrollingReasons();
+void WebLayerImpl::clearMainThreadScrollingReasons(
+    uint32_t main_thread_scrolling_reasons_to_clear) {
+  layer_->ClearMainThreadScrollingReasons(
+      main_thread_scrolling_reasons_to_clear);
+}
+
+uint32_t WebLayerImpl::mainThreadScrollingReasons() {
+  return layer_->main_thread_scrolling_reasons();
 }
 
 bool WebLayerImpl::shouldScrollOnMainThread() const {