cc : Track ids for which active opacity always wins on property trees

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index 264af100de4932b8c495fbeb8d4f0f65a64cbe2f..402a94ec3955b520b8f2caf9f2b6f00779e29798 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -2887,6 +2887,9 @@ class LayerTreeHostImplTestScrollbarOpacity : public LayerTreeHostImplTest {
     EffectNode* pending_tree_node =
         host_impl_->pending_tree()->property_trees()->effect_tree.Node(
             scrollbar_layer->effect_tree_index());
+    host_impl_->pending_tree()
+        ->property_trees()
+        ->always_use_active_tree_opacity_effect_ids.push_back(400);
     EXPECT_FLOAT_EQ(1.f, active_tree_node->data.opacity);
     EXPECT_FLOAT_EQ(1.f, scrollbar_layer->opacity());
     EXPECT_FLOAT_EQ(0.f, pending_tree_node->data.opacity);