cc : Simplify layer skipping logic

cc/trees/draw_property_utils.cc

Index: cc/trees/draw_property_utils.cc
diff --git a/cc/trees/draw_property_utils.cc b/cc/trees/draw_property_utils.cc
index 27ef742570cf0370b73c3065465b1c4e44630450..7d22b7b3b377b7ce53eaeea0ebc8f251cc05945b 100644
--- a/cc/trees/draw_property_utils.cc
+++ b/cc/trees/draw_property_utils.cc
@@ -282,7 +282,6 @@ static inline bool TransformToScreenIsKnown(LayerImpl* layer,
 
 template <typename LayerType>
 static bool LayerNeedsUpdateInternal(LayerType* layer,
-                                     bool layer_is_drawn,
                                      const TransformTree& tree) {
   // Layers can be skipped if any of these conditions are met.
   //   - is not drawn due to it or one of its ancestors being hidden (or having
@@ -300,9 +299,6 @@ static bool LayerNeedsUpdateInternal(LayerType* layer,
   // Note, if the layer should not have been drawn due to being fully
   // transparent, we would have skipped the entire subtree and never made it
   // into this function, so it is safe to omit this check here.
-  if (!layer_is_drawn)
-    return false;
-
   if (!layer->DrawsContent() || layer->bounds().IsEmpty())
     return false;
 
@@ -328,15 +324,11 @@ void FindLayersThatNeedUpdates(LayerTreeImpl* layer_tree_impl,
                                LayerImplList* update_layer_list,
                                std::vector<LayerImpl*>* visible_layer_list) {
   for (auto* layer_impl : *layer_tree_impl) {
-    bool layer_is_drawn =
-        effect_tree.Node(layer_impl->effect_tree_index())->data.is_drawn;
-
     if (!IsRootLayer(layer_impl) &&
-        LayerShouldBeSkipped(layer_impl, layer_is_drawn, transform_tree,
-                             effect_tree))
+        LayerShouldBeSkipped(layer_impl, transform_tree, effect_tree))
       continue;
 
-    if (LayerNeedsUpdate(layer_impl, layer_is_drawn, transform_tree)) {
+    if (LayerNeedsUpdate(layer_impl, transform_tree)) {
       visible_layer_list->push_back(layer_impl);
       update_layer_list->push_back(layer_impl);
     }
@@ -378,88 +370,36 @@ void UpdateRenderSurfacesForLayersRecursive(EffectTree* effect_tree,
 
 }  // namespace
 
-static inline bool LayerShouldBeSkipped(Layer* layer,
-                                        bool layer_is_drawn,
-                                        const TransformTree& transform_tree,
-                                        const EffectTree& effect_tree) {
+template <typename LayerType>
+static inline bool LayerShouldBeSkippedInternal(
+    LayerType* layer,
+    const TransformTree& transform_tree,
+    const EffectTree& effect_tree) {
   const TransformNode* transform_node =
       transform_tree.Node(layer->transform_tree_index());
   const EffectNode* effect_node = effect_tree.Node(layer->effect_tree_index());
 
-  // If the layer transform is not invertible, it should not be drawn.
-  if (!transform_node->data.node_and_ancestors_are_animated_or_invertible)
-    return true;
-
-  // When we need to do a readback/copy of a layer's output, we can not skip
-  // it or any of its ancestors.
-  if (effect_node->data.num_copy_requests_in_subtree > 0)
-    return false;
-
-  // If the layer is not drawn, then skip it and its subtree.
-  if (!effect_node->data.is_drawn)
-    return true;
-
-  if (!transform_node->data.to_screen_is_potentially_animated &&
-      effect_node->data.hidden_by_backface_visibility)
-    return true;
-
-  // If layer has a background filter, don't skip the layer, even it the
-  // opacity is 0.
-  if (effect_node->data.node_or_ancestor_has_background_filters)
-    return false;
-
-  // If the opacity is being animated then the opacity on the main thread is
-  // unreliable (since the impl thread may be using a different opacity), so it
-  // should not be trusted.
-  // In particular, it should not cause the subtree to be skipped.
-  // Similarly, for layers that might animate opacity using an impl-only
-  // animation, their subtree should also not be skipped.
-  return !effect_node->data.screen_space_opacity &&
-         !effect_node->data.to_screen_opacity_is_animated;
+  bool layer_is_drawn = effect_tree.property_trees()->is_active
+                            ? effect_node->data.is_drawn_on_active
+                            : effect_node->data.is_drawn_on_main_and_pending;
+  // If the layer transform is not invertible, it should be skipped.
+  // TODO(ajuma): Correctly process subtrees with singular transform for the
+  // case where we may animate to a non-singular transform and wish to
+  // pre-raster.
+  return !transform_node->data.node_and_ancestors_are_animated_or_invertible ||
+         effect_node->data.hidden_by_backface_visibility || !layer_is_drawn;
 }
 
 bool LayerShouldBeSkipped(LayerImpl* layer,
-                          bool layer_is_drawn,
                           const TransformTree& transform_tree,
                           const EffectTree& effect_tree) {
-  const TransformNode* transform_node =
-      transform_tree.Node(layer->transform_tree_index());
-  const EffectNode* effect_node = effect_tree.Node(layer->effect_tree_index());
-  // If the layer transform is not invertible, it should not be drawn.
-  // TODO(ajuma): Correctly process subtrees with singular transform for the
-  // case where we may animate to a non-singular transform and wish to
-  // pre-raster.
-  if (!transform_node->data.node_and_ancestors_are_animated_or_invertible)
-    return true;
-
-  // When we need to do a readback/copy of a layer's output, we can not skip
-  // it or any of its ancestors.
-  if (effect_node->data.num_copy_requests_in_subtree > 0)
-    return false;
-
-  // If the layer is not drawn, then skip it and its subtree.
-  if (!effect_node->data.is_drawn)
-    return true;
-
-  if (effect_node->data.hidden_by_backface_visibility)
-    return true;
-
-  // If layer is on the pending tree and opacity is being animated then
-  // this subtree can't be skipped as we need to create, prioritize and
-  // include tiles for this layer when deciding if tree can be activated.
-  if (!transform_tree.property_trees()->is_active &&
-      effect_node->data.to_screen_opacity_is_animated)
-    return false;
-
-  // If layer has a background filter, don't skip the layer, even it the
-  // opacity is 0.
-  if (effect_node->data.node_or_ancestor_has_background_filters)
-    return false;
+  return LayerShouldBeSkippedInternal(layer, transform_tree, effect_tree);
+}
 
-  // The opacity of a layer always applies to its children (either implicitly
-  // via a render surface or explicitly if the parent preserves 3D), so the
-  // entire subtree can be skipped if this layer is fully transparent.
-  return !effect_node->data.screen_space_opacity;
+bool LayerShouldBeSkipped(Layer* layer,
+                          const TransformTree& transform_tree,
+                          const EffectTree& effect_tree) {
+  return LayerShouldBeSkippedInternal(layer, transform_tree, effect_tree);
 }
 
 void FindLayersThatNeedUpdates(LayerTreeHost* layer_tree_host,
@@ -469,15 +409,11 @@ void FindLayersThatNeedUpdates(LayerTreeHost* layer_tree_host,
   LayerTreeHostCommon::CallFunctionForEveryLayer(
       layer_tree_host,
       [&](Layer* layer) {
-        bool layer_is_drawn =
-            effect_tree.Node(layer->effect_tree_index())->data.is_drawn;
-
         if (!IsRootLayer(layer) &&
-            LayerShouldBeSkipped(layer, layer_is_drawn, transform_tree,
-                                 effect_tree))
+            LayerShouldBeSkipped(layer, transform_tree, effect_tree))
           return;
 
-        if (LayerNeedsUpdate(layer, layer_is_drawn, transform_tree)) {
+        if (LayerNeedsUpdate(layer, transform_tree)) {
           update_layer_list->push_back(layer);
         }
 
@@ -776,15 +712,13 @@ void ComputeVisibleRects(LayerImpl* root_layer,
 }
 
 bool LayerNeedsUpdate(Layer* layer,
-                      bool layer_is_drawn,
                       const TransformTree& tree) {
-  return LayerNeedsUpdateInternal(layer, layer_is_drawn, tree);
+  return LayerNeedsUpdateInternal(layer, tree);
 }
 
 bool LayerNeedsUpdate(LayerImpl* layer,
-                      bool layer_is_drawn,
                       const TransformTree& tree) {
-  return LayerNeedsUpdateInternal(layer, layer_is_drawn, tree);
+  return LayerNeedsUpdateInternal(layer, tree);
 }
 
 gfx::Transform DrawTransform(const LayerImpl* layer,