cc : Stop pushing layers from hidden subtrees at commit

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 11a354ab33e91e5fba1808882b707e6504131573..ce808d4b6c8e96f35e9f517d8b636502c8318b72 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -1070,6 +1070,8 @@ bool LayerTreeHost::PaintContent(const LayerList& update_layer_list,
 }
 
 void LayerTreeHost::AddLayerShouldPushProperties(Layer* layer) {
+  if (layer->is_hidden())

[enne (OOO), 2017/05/01 20:15:09]

This is a little awkward, here.  I think what you want to say is that if a layer
is hidden, it shouldn't push properties.  This says if a layer becomes hidden,
then ignore additional push properties requests.  I think those are not quite
the same?

And then the tree sychronizer redundantly fixes this up, so maybe this call
isn't needed here?

[jaydasika, 2017/05/01 23:41:39]

Yes, what we want to say is if a layer is hidden, it shouldn't push properties.

The reason I added this here is for this sequence : hide layer-> commit ->
change a property on hidden layer -> commit. 
Even during second commit, we don't want to push properties of the layer. But if
the layer tree topology hasn't changed, we won't do full tree sync and never hit
the code in tree synchronizer that deletes hidden layers from push properties
layer list.

I agree this is unnecessarily complex, maybe we should just check while pushing
properties if the layer is hidden and skip it there. 
    

[enne (OOO), 2017/05/02 01:46:01]

That sounds good!

[jaydasika, 2017/05/19 19:08:59]

Done.

+    return;
   layers_that_should_push_properties_.insert(layer);
 }