Add screen space opacity to opacity tree

Screen space opacity is required to compute if a layer can use lcd text using property trees.
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1209213002

Cr-Commit-Position: refs/heads/master@{#336474}
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index bc61a2a..cde5339 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -791,7 +791,8 @@
     OpacityTree& opacity_tree =
         layer_tree_impl()->property_trees()->opacity_tree;
     OpacityNode* node = opacity_tree.Node(opacity_tree_index_);
-    node->data = opacity_;
+    node->data.opacity = opacity_;
+    opacity_tree.set_needs_update(true);
   }
 }