cc : Store surface layer ids on LayerTreeHost and push them at commit

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1613 matching lines @@
         !OuterViewportScrollLayer()->user_scrollable_horizontal();
     metadata.root_overflow_y_hidden =
         !OuterViewportScrollLayer()->user_scrollable_vertical();
   }
 
   if (GetDrawMode() == DRAW_MODE_RESOURCELESS_SOFTWARE) {
     metadata.is_resourceless_software_draw_with_scroll_or_animation =
         IsActivelyScrolling() || mutator_host_->NeedsTickAnimations();
   }
 
-  for (LayerImpl* surface_layer : active_tree_->SurfaceLayers()) {
-    SurfaceLayerImpl* surface_layer_impl =
-        static_cast<SurfaceLayerImpl*>(surface_layer);
-    if (settings_.enable_surface_synchronization) {
-      if (surface_layer_impl->fallback_surface_info().is_valid()) {
-        metadata.referenced_surfaces.push_back(
-            surface_layer_impl->fallback_surface_info().id());
-      }
-    } else {
-      metadata.referenced_surfaces.push_back(
-          surface_layer_impl->primary_surface_info().id());
-    }
+  for (auto& surface_id : active_tree_->SurfaceLayerIds()) {
+    metadata.referenced_surfaces.push_back(surface_id);
   }
+
   if (!InnerViewportScrollLayer())
     return metadata;
 
   metadata.root_overflow_x_hidden |=
       !InnerViewportScrollLayer()->user_scrollable_horizontal();
   metadata.root_overflow_y_hidden |=
       !InnerViewportScrollLayer()->user_scrollable_vertical();
 
   // TODO(miletus) : Change the metadata to hold ScrollOffset.
   metadata.root_scroll_offset =
@@ skipping 2699 matching lines @@
 
 void LayerTreeHostImpl::ShowScrollbarsForImplScroll(ElementId element_id) {
   if (!element_id)
     return;
   if (ScrollbarAnimationController* animation_controller =
           ScrollbarAnimationControllerForElementId(element_id))
     animation_controller->DidScrollUpdate();
 }
 
 }  // namespace cc