Document some transform node animation fields.

cc/trees/transform_node.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TREES_TRANSFORM_NODE_H_
 #define CC_TREES_TRANSFORM_NODE_H_
 
 #include "cc/cc_export.h"
 #include "ui/gfx/geometry/point_f.h"
 #include "ui/gfx/geometry/scroll_offset.h"
@@ skipping 51 matching lines @@
   int source_node_id;
 
   // This id determines which 3d rendering context the node is in. 0 is a
   // special value and indicates that the node is not in any 3d rendering
   // context.
   int sorting_context_id;
 
   // TODO(vollick): will be moved when accelerated effects are implemented.
   bool needs_local_transform_update : 1;
 
+  // Whether this node or any ancestor has a potentially running
+  // (i.e., irrespective of exact timeline) transform animation or an
+  // invertible transform.
   bool node_and_ancestors_are_animated_or_invertible : 1;
 
   bool is_invertible : 1;
+  // Whether the transform from this node to the screen is
+  // invertible.
   bool ancestors_are_invertible : 1;
 
+  // Whether this node has a potentially running (i.e., irrespective
+  // of exact timeline) transform animation.
   bool has_potential_animation : 1;
+  // Whether this node has a currently running transform animation.
   bool is_currently_animating : 1;
+  // Whether this node *or an ancestor* has a potentially running
+  // (i.e., irrespective of exact timeline) transform
+  // animation.
   bool to_screen_is_potentially_animated : 1;
+  // Whether all animations on this transform node are simple
+  // translations.
   bool has_only_translation_animations : 1;
 
   // Flattening, when needed, is only applied to a node's inherited transform,
   // never to its local transform.
   bool flattens_inherited_transform : 1;
 
   // This is true if the to_parent transform at every node on the path to the
   // root is flat.
   bool node_and_ancestors_are_flat : 1;
 
@@ skipping 60 matching lines @@
   gfx::Transform to_screen;
 
   bool is_showing_backface : 1;
 
   bool operator==(const TransformCachedNodeData& other) const;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_TRANSFORM_NODE_H_