Rebuild PropertyTrees When Layer Attach to New LayerTreeHost

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index af3fc67471c847f0d6fbaf5dadc00d0838b983e5..4f799b8ce0b0d3a87be19069fcb0fa0410cf961f 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -132,6 +132,11 @@ void Layer::SetLayerTreeHost(LayerTreeHost* host) {
   if (layer_tree_host_)
     layer_tree_host_->property_trees()->needs_rebuild = true;
 
+  if (host)
+    host->property_trees()->needs_rebuild = true;
+
+  InvalidatePropertyTreesIndices();

[Ian Vollick, 2015/06/09 00:18:51]

Is there a chance that we're detaching/attaching a subtree rather than a single
layer?

If we'll never have a tiny subtree, then please DCHECK that there can be no
children.

If we could have a subtree, then you're looking at a walk over that subtree to
set all the indices to -1 which would be unfortunate -- the sequence numbers
were added so we could avoid that very thing
(https://code.google.com/p/chromium/codesearch#chromium/src/cc/layers/layer.cc...).
It seems like setting needs_rebuild = true implies that all the indices are
dirty. Perhaps PropertyTrees should stop being a dumb struct and define a
SetNeedsRebuild fn that sets the needs rebuild bit as well as bumping the
sequence number?

+
   layer_tree_host_ = host;
 
   // When changing hosts, the layer needs to commit its properties to the impl
@@ -1053,6 +1058,13 @@ int Layer::opacity_tree_index() const {
   return opacity_tree_index_;
 }
 
+void Layer::InvalidatePropertyTreesIndices() {
+  int invalid_property_tree_index = -1;
+  SetTransformTreeIndex(invalid_property_tree_index);
+  SetClipTreeIndex(invalid_property_tree_index);
+  SetOpacityTreeIndex(invalid_property_tree_index);
+}
+
 void Layer::SetShouldFlattenTransform(bool should_flatten) {
   DCHECK(IsPropertyChangeAllowed());
   if (should_flatten_transform_ == should_flatten)