cc : Workaround for null layer impls and invalid property tree indices

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 17d676f1a85b419dc24a79a046fc5ec08812ae0d..7e643e89d63d5e186af38ef175b81340335a5152 100644
--- a/cc/trees/draw_property_utils.cc
+++ b/cc/trees/draw_property_utils.cc
@@ -458,9 +458,19 @@ static inline bool LayerShouldBeSkippedInternal(
       transform_tree.Node(layer->transform_tree_index());
   const EffectNode* effect_node = effect_tree.Node(layer->effect_tree_index());
 
+  DCHECK(effect_node);
+  DCHECK(transform_node);
+  // TODO(crbug.com/726423) : This is a workaround for crbug.com/726225 to
+  // avoid crashing when there is no effect or transform node. Effect node and
+  // transform node should always exist here and this workaround should be
+  // removed.
+  if (!transform_node || !effect_node)
+    return true;
+
   if (effect_node->has_render_surface &&
       effect_node->num_copy_requests_in_subtree > 0)
     return false;
+
   // 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
@@ -851,6 +861,13 @@ void FindLayersThatNeedUpdates(LayerTreeImpl* layer_tree_impl,
   const EffectTree& effect_tree = property_trees->effect_tree;
 
   for (auto* layer_impl : *layer_tree_impl) {
+    DCHECK(layer_impl);
+    DCHECK(layer_impl->layer_tree_impl());
+    // TODO(crbug.com/726423) : This is a workaround for crbug.com/725851 to
+    // avoid crashing when layer_impl is nullptr. This workaround should be
+    // removed as layer_impl should not be nullptr here.
+    if (!layer_impl)
+      continue;
     if (!IsRootLayer(layer_impl) &&
         LayerShouldBeSkipped(layer_impl, transform_tree, effect_tree))
       continue;