Update cc effect node documentation.

cc/trees/property_tree_builder.cc

Index: cc/trees/property_tree_builder.cc
diff --git a/cc/trees/property_tree_builder.cc b/cc/trees/property_tree_builder.cc
index f539966fa199a80c8bbbbd6e473f4d8a360111bc..d54ae5c75844fca23cdd92127d4a94e1264d50c5 100644
--- a/cc/trees/property_tree_builder.cc
+++ b/cc/trees/property_tree_builder.cc
@@ -948,10 +948,12 @@ bool AddEffectNodeIfNeeded(
     }
     node->clip_id = data_from_ancestor.clip_tree_parent;
   } else {
-    // Root render surface acts the unbounded and untransformed to draw content
-    // into. Transform node created from root layer (includes device scale
-    // factor) and clip node created from root layer (include viewports) applies
-    // to root render surface's content, but not root render surface itself.
+    // The root render surface acts as the unbounded and untransformed
+    // surface into which content is drawn. The transform node created
+    // from the root layer (which includes device scale factor) and
+    // the clip node created from the root layer (which includes
+    // viewports) apply to the root render surface's content, but not
+    // to the root render surface itself.
     node->transform_id = TransformTree::kRootNodeId;
     node->clip_id = ClipTree::kViewportNodeId;
   }