Apply filter mutation to effect tree directly for SPv2.

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 2b51bb3dacb6345f189c701540579dbad7652ff1..7402ea2a808697928a1a96edc44562b899aa6efc 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -1263,6 +1263,13 @@ void LayerTreeHost::SetMutatorsNeedRebuildPropertyTrees() {
 void LayerTreeHost::SetElementFilterMutated(ElementId element_id,

[wkorman, 2017/05/10 22:24:25]

Commenting out the entire implementation of this method doesn't appear to cause
any tests to fail in cc_unittests, webkit_unit_tests, or
blink_platform_unittests.

It also doesn't appear to cause any layout tests to fail under:

% ./third_party/WebKit/Tools/Scripts/run-webkit-tests animations transitions
compositing virtual/threaded/animations virtual/threaded/transitions
virtual/threaded/compositing

Am adding NOTREACHED() and will look at writing test case that should execute
this code path.

                                             ElementListType list_type,
                                             const FilterOperations& filters) {
+  if (settings_.use_layer_lists) {
+    // In SPv2 we always have property trees and can set the filter
+    // directly on the effect node.
+    property_trees_.effect_tree.OnFilterAnimated(element_id, filters);
+    return;
+  }
+
   Layer* layer = LayerByElementId(element_id);
   DCHECK(layer);
   layer->OnFilterAnimated(filters);