[NOT FOR REVIEW] cc : New clip 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 d99262f84e268156ac925bafd5a8b9ef5092d462..8d42ab09bce1e9e23234d2a23e12ebd0fac77439 100644
--- a/cc/trees/property_tree_builder.cc
+++ b/cc/trees/property_tree_builder.cc
@@ -456,6 +456,81 @@ void AddClipNodeIfNeeded(const DataForRecursion<LayerType>& data_from_ancestor,
 }
 
 template <typename LayerType>
+void AddClipNodeOnlyIfLayerClipsSubtree(
+    const DataForRecursion<LayerType>& data_from_ancestor,
+    LayerType* layer,
+    bool created_render_surface,
+    bool created_transform_node,
+    DataForRecursion<LayerType>* data_for_children) {
+  const bool inherits_clip = !ClipParent(layer);
+  const int parent_id = inherits_clip ? data_from_ancestor.clip_tree_parent
+                                      : ClipParent(layer)->clip_tree_index();
+  ClipNode* parent =
+      data_from_ancestor.property_trees->clip_tree.Node(parent_id);
+
+  bool apply_ancestor_clip = false;
+  if (inherits_clip) {
+    apply_ancestor_clip = data_from_ancestor.apply_ancestor_clip;
+  } else {
+    const EffectNode* parent_effect_node =
+        data_from_ancestor.property_trees->effect_tree.Node(
+            ClipParent(layer)->effect_tree_parent());
+    if (parent_effect_node->clip_id == parent->id) {
+      if (parent_effect_node->surface_is_clipped) {
+        // In this case, there is no clipping layer between the clip parent and
+        // its target and the target has applied the clip.
+        apply_ancestor_clip = false;
+      } else {
+        // In this case, there is no clipping layer between the clip parent and
+        // its target and the target has not applied the clip. There are two
+        // cases when a target doesn't apply clip. First, there is no ancestor
+        // clip to apply, in this case apply_ancestor_clip should be false.
+        // Second, there is a clip to apply but there are unclipped descendants,
+        // so the target cannot apply the clip. In this case,
+        // apply_ancestor_clip should be true.
+        apply_ancestor_clip = parent_effect_node->has_unclipped_descendants;
+      }
+    } else {
+      // In this case, there is a clipping layer between the clip parent and
+      // its target.
+      apply_ancestor_clip = true;
+    }
+  }
+  if (created_render_surface)
+    SetSurfaceIsClipped(data_for_children, apply_ancestor_clip, layer);
+
+  bool layer_clips_subtree = LayerClipsSubtree(layer);
+  if (layer_clips_subtree) {
+    data_for_children->apply_ancestor_clip = true;
+  }
+
+  if (!layer_clips_subtree) {
+    data_for_children->clip_tree_parent = parent_id;
+  } else {
+    LayerType* transform_parent = data_for_children->transform_tree_parent;
+    if (PositionConstraint(layer).is_fixed_position() &&
+        !created_transform_node) {
+      transform_parent = data_for_children->transform_fixed_parent;
+    }
+    ClipNode node;
+    node.clip = gfx::RectF(gfx::PointF() + layer->offset_to_transform_parent(),
+                           gfx::SizeF(layer->bounds()));
+    node.transform_id = transform_parent->transform_tree_index();
+    node.owner_id = layer->id();
+    if (layer_clips_subtree)
+      node.clip_type = ClipNode::ClipType::APPLIES_LOCAL_CLIP;
+    else
+      node.clip_type = ClipNode::ClipType::NONE;
+    data_for_children->clip_tree_parent =
+        data_for_children->property_trees->clip_tree.Insert(node, parent_id);
+    data_for_children->property_trees->clip_id_to_index_map[layer->id()] =
+        data_for_children->clip_tree_parent;
+  }
+
+  layer->SetClipTreeIndex(data_for_children->clip_tree_parent);
+}
+
+template <typename LayerType>
 static inline bool IsAtBoundaryOf3dRenderingContext(LayerType* layer) {
   return Parent(layer)
              ? Parent(layer)->sorting_context_id() !=