cc: Don't create SyncedPropety instances on the main thread.

cc/trees/layer_tree_host_in_process.cc

Index: cc/trees/layer_tree_host_in_process.cc
diff --git a/cc/trees/layer_tree_host_in_process.cc b/cc/trees/layer_tree_host_in_process.cc
index 1f0eab1c21a0057bf87c4b5ca19c9d359912efb9..8d5ba2d695d971b61183835ebbb277fe2a83bd85 100644
--- a/cc/trees/layer_tree_host_in_process.cc
+++ b/cc/trees/layer_tree_host_in_process.cc
@@ -359,7 +359,8 @@ void LayerTreeHostInProcess::FinishCommitOnImplThread(
 
     // This must happen after synchronizing property trees and after pushing
     // properties, which updates the clobber_active_value flag.
-    sync_tree->UpdatePropertyTreeScrollOffset(layer_tree_->property_trees());
+    sync_tree->property_trees()->scroll_tree.PushScrollUpdatesFromMainThread(
+        layer_tree_->property_trees(), sync_tree);
 
     // This must happen after synchronizing property trees and after push
     // properties, which updates property tree indices, but before animation