cc : Simplify layer skipping logic

cc/trees/property_tree.cc

Index: cc/trees/property_tree.cc
diff --git a/cc/trees/property_tree.cc b/cc/trees/property_tree.cc
index 54f4ec47496a50ce1f32c6c0ef4d220859a6c18c..1e2412275b4cd70233eb4f462e90e0200482d893 100644
--- a/cc/trees/property_tree.cc
+++ b/cc/trees/property_tree.cc
@@ -1244,11 +1244,12 @@ void EffectTree::UpdateIsDrawn(EffectNode* node, EffectNode* parent_node) {
   // 1) Nodes that contribute to copy requests, whether hidden or not, must be
   //    drawn.
   // 2) Nodes that have a background filter.
-  // 3) Nodes with animating screen space opacity are drawn if their parent is
-  //    drawn irrespective of their opacity.
+  // 3) Nodes with animating screen space opacity on main thread or pending tree
+  //    are drawn if their parent is drawn irrespective of their opacity.
   if (node->data.has_copy_request)
     node->data.is_drawn = true;
-  else if (node->data.opacity == 0.f && !node->data.has_animated_opacity &&
+  else if (node->data.opacity == 0.f &&
+           (!node->data.has_animated_opacity || property_trees()->is_active) &&

[ajuma, 2016/04/12 21:48:14]

What if nothing triggers a property tree update on the active tree? (That is,
say we push property trees from the pending tree to the active tree, and there's
no animation to make needs_update true on the effect tree.)

[jaydasika, 2016/04/13 00:13:42]

Split this into 2 bools to handle the case.

[ajuma, 2016/04/13 14:33:15]

Hmm. Given that the effect tree is likely to only have a small number of nodes,
how about just setting needs_update to true on it when setting it on the pending
tree? (This keeps the code simpler and avoids growing nodes for things we can
easily recompute.)

[jaydasika, 2016/04/13 18:48:42]

Done.

            !node->data.has_background_filters)
     node->data.is_drawn = false;
   else if (parent_node)