Track transform animation content readiness on TransformNode.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 54dc7bbd336bc73f606cdad27254392eed83b148..1095bd11b56a788350e450e0c3c078ffd9ea82f4 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -943,12 +943,15 @@ DrawResult LayerTreeHostImpl::CalculateRenderPasses(FrameData* frame) {
           append_quads_data.checkerboarded_no_recording_content_area;
       checkerboarded_needs_raster_content_area +=
           append_quads_data.checkerboarded_needs_raster_content_area;
+      TransformNode* transform_node =
+          active_tree()->property_trees()->transform_tree.Node(
+              layer->transform_tree_index());

[wkorman, 2017/05/20 01:31:27]

Are we assured that we will always have a transform node, or do we need to check
for TransformTree::kInvalidNodeId?

[pdr., 2017/05/22 17:03:34]

We've had a bunch of crashes in this area recently (crbug.com/712298,
crbug.com/708951, crbug.com/721772). That said, I think we should not guard
against this in new code, especially now that we better understand this area.
LGTM for leaving this as-is without checking for a transform node.

       if (append_quads_data.num_missing_tiles > 0) {
         have_missing_animated_tiles |=
-            !layer->was_ever_ready_since_last_transform_animation() ||
+            !transform_node->ready_since_animation ||
             layer->screen_space_transform_is_animating();
       } else {
-        layer->set_was_ever_ready_since_last_transform_animation(true);
+        transform_node->ready_since_animation = true;

[jaydasika, 2017/05/22 18:11:29]

As layer->transform node is not 1:1, you can't do this here. The value of
ready_since_animation with this logic would depend on the num_missing_tiles
value of the last layer referencing that transform node (this function iterates
through all drawn layers). So, we need to have this on layers.

Since the aim here is to remove layer references from
LayerTreeImpl::SetTransformMutated, we could have a field for this on both
transform node and layer. So, you would update the field on transform node in
LayerTreeImpl::SetTransformMutated and the field on layer here and the actual
value of ready_since_animation would be inferred from both (this would be
similar to how we do damage tracking where we have both
LayerImpl::layer_property_changed and TransformNode::transform_changed).

       }
     }
     frame->activation_dependencies.insert(
@@ -4235,12 +4238,7 @@ void LayerTreeHostImpl::ElementIsAnimatingChanged(
                                                              list_type);
             property_trees->transform_tree.set_needs_update(true);
             tree->set_needs_update_draw_properties();
-            // TODO(crbug.com/702777):
-            // was_ever_ready_since_last_transform_animation should not live on
-            // layers.
-            if (LayerImpl* layer = tree->LayerByElementId(element_id)) {
-              layer->set_was_ever_ready_since_last_transform_animation(false);
-            }
+            transform_node->ready_since_animation = false;
           }
         }
         break;