Revert of cc : Remove subtree skipping in LayerTreeHostCommon

cc/trees/layer_tree_host_common.cc

Index: cc/trees/layer_tree_host_common.cc
diff --git a/cc/trees/layer_tree_host_common.cc b/cc/trees/layer_tree_host_common.cc
index f1a5fc4d846fe4619d19d63b08d9db8f148af2ca..9485a644f32f8a9baff48a6c247be5eb35d4a2dc 100644
--- a/cc/trees/layer_tree_host_common.cc
+++ b/cc/trees/layer_tree_host_common.cc
@@ -542,28 +542,29 @@ void CalculateRenderTarget(LayerImpl* layer,
                                                 property_trees->transform_tree,
                                                 property_trees->effect_tree)) {
     layer->draw_properties().render_target = nullptr;
-  } else {
-    bool render_to_separate_surface =
-        IsRootLayer(layer) ||
-        (can_render_to_separate_surface && layer->render_surface());
+    return;
+  }
 
-    if (render_to_separate_surface) {
-      DCHECK(layer->render_surface()) << IsRootLayer(layer)
-                                      << can_render_to_separate_surface
-                                      << layer->has_render_surface();
-      layer->draw_properties().render_target = layer;
+  bool render_to_separate_surface =
+      IsRootLayer(layer) ||
+      (can_render_to_separate_surface && layer->render_surface());
 
-      if (layer->mask_layer())
-        layer->mask_layer()->draw_properties().render_target = layer;
+  if (render_to_separate_surface) {
+    DCHECK(layer->render_surface()) << IsRootLayer(layer)
+                                    << can_render_to_separate_surface
+                                    << layer->has_render_surface();
+    layer->draw_properties().render_target = layer;
 
-      if (layer->replica_layer() && layer->replica_layer()->mask_layer())
-        layer->replica_layer()->mask_layer()->draw_properties().render_target =
-            layer;
+    if (layer->mask_layer())
+      layer->mask_layer()->draw_properties().render_target = layer;
 
-    } else {
-      DCHECK(!IsRootLayer(layer));
-      layer->draw_properties().render_target = layer->parent()->render_target();
-    }
+    if (layer->replica_layer() && layer->replica_layer()->mask_layer())
+      layer->replica_layer()->mask_layer()->draw_properties().render_target =
+          layer;
+
+  } else {
+    DCHECK(!IsRootLayer(layer));
+    layer->draw_properties().render_target = layer->parent()->render_target();
   }
   for (size_t i = 0; i < layer->children().size(); ++i) {
     CalculateRenderTarget(
@@ -610,13 +611,6 @@ void CalculateRenderSurfaceLayerList(
     if (layer->render_surface())
       layer->ClearRenderSurfaceLayerList();
     layer->draw_properties().render_target = nullptr;
-    for (auto* child_layer : layer->children()) {
-      CalculateRenderSurfaceLayerList(
-          child_layer, property_trees, render_surface_layer_list, descendants,
-          nearest_occlusion_immune_ancestor, layer_is_drawn,
-          can_render_to_separate_surface, current_render_surface_layer_list_id,
-          max_texture_size);
-    }
     return;
   }
 
@@ -663,10 +657,11 @@ void CalculateRenderSurfaceLayerList(
     descendants = &(layer->render_surface()->layer_list());
   }
 
+  size_t descendants_size = descendants->size();
+
   bool layer_should_be_skipped = !draw_property_utils::LayerNeedsUpdate(
       layer, layer_is_drawn, property_trees->transform_tree);
   if (!layer_should_be_skipped) {
-    DCHECK(layer->draw_properties().render_target);
     MarkLayerWithRenderSurfaceLayerListId(layer,
                                           current_render_surface_layer_list_id);
     descendants->push_back(layer);
@@ -745,7 +740,7 @@ void CalculateRenderSurfaceLayerList(
       layer->render_surface()->SetContentRect(surface_content_rect);
     }
     const LayerImpl* parent_target = layer->parent()->render_target();
-    if (parent_target && !IsRootLayer(parent_target)) {
+    if (!IsRootLayer(parent_target)) {
       gfx::Rect surface_content_rect =
           parent_target->render_surface()->accumulated_content_rect();
       if (render_to_separate_surface) {
@@ -773,6 +768,13 @@ void CalculateRenderSurfaceLayerList(
   if (render_to_separate_surface && !IsRootLayer(layer) &&
       layer->render_surface()->DrawableContentRect().IsEmpty()) {
     RemoveSurfaceForEarlyExit(layer, render_surface_layer_list);
+    return;
+  }
+
+  // If neither this layer nor any of its children were added, early out.
+  if (descendants_size == descendants->size()) {
+    DCHECK(!render_to_separate_surface || IsRootLayer(layer));
+    return;
   }
 }
 
@@ -873,6 +875,8 @@ void CalculateDrawPropertiesInternal(
   DCHECK(inputs->can_render_to_separate_surface ==
          inputs->property_trees->non_root_surfaces_enabled);
   const bool subtree_visible_from_ancestor = true;
+  for (auto* layer : *inputs->root_layer->layer_tree_impl())
+    layer->draw_properties().render_target = nullptr;
   CalculateRenderTarget(inputs->root_layer, inputs->property_trees,
                         subtree_visible_from_ancestor,
                         inputs->can_render_to_separate_surface);