cc: Move SyncedScrollOffset to scroll tree

cc/trees/property_tree_builder.cc

Index: cc/trees/property_tree_builder.cc
diff --git a/cc/trees/property_tree_builder.cc b/cc/trees/property_tree_builder.cc
index 551c9112f8fe0a9c9043f88e0d4160abfa782914..9c6eae7f847b894e866053c076b07f6447a81c2b 100644
--- a/cc/trees/property_tree_builder.cc
+++ b/cc/trees/property_tree_builder.cc
@@ -713,6 +713,11 @@ void AddScrollNodeIfNeeded(
         node.data.main_thread_scrolling_reasons;
     data_for_children->scroll_tree_parent_created_by_uninheritable_criteria =
         scroll_node_uninheritable_criteria;
+
+    if (node.data.scrollable) {
+      data_for_children->scroll_tree->synced_scroll_offset(layer->id())
+          ->PushFromMainThread(layer->scroll_offset());
+    }
   }
 
   layer->SetScrollTreeIndex(data_for_children->scroll_tree_parent);
@@ -940,6 +945,8 @@ void PropertyTreeBuilder::BuildPropertyTrees(
     const gfx::Rect& viewport,
     const gfx::Transform& device_transform,
     PropertyTrees* property_trees) {
+  property_trees->is_main_thread = true;
+  property_trees->is_active = false;
   BuildPropertyTreesTopLevelInternal(
       root_layer, page_scale_layer, inner_viewport_scroll_layer,
       outer_viewport_scroll_layer, overscroll_elasticity_layer,
@@ -959,6 +966,8 @@ void PropertyTreeBuilder::BuildPropertyTrees(
     const gfx::Rect& viewport,
     const gfx::Transform& device_transform,
     PropertyTrees* property_trees) {
+  property_trees->is_main_thread = false;
+  property_trees->is_active = root_layer->IsActive();
   BuildPropertyTreesTopLevelInternal(
       root_layer, page_scale_layer, inner_viewport_scroll_layer,
       outer_viewport_scroll_layer, overscroll_elasticity_layer,