Update cc effect node documentation.

cc/trees/effect_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_EFFECT_NODE_H_
 #define CC_TREES_EFFECT_NODE_H_
 
 #include "cc/base/filter_operations.h"
 #include "cc/cc_export.h"
 #include "third_party/skia/include/core/SkBlendMode.h"
@@ skipping 33 matching lines @@
   gfx::Size unscaled_mask_target_size;
 
   bool has_render_surface;
   bool has_copy_request;
   bool hidden_by_backface_visibility;
   bool double_sided;
   bool is_drawn;
   // TODO(jaydasika) : Delete this after implementation of
   // SetHideLayerAndSubtree is cleaned up. (crbug.com/595843)
   bool subtree_hidden;
+  // Whether this node has a potentially running (i.e., irrespective
+  // of exact timeline) filter animation.
   bool has_potential_filter_animation;

[pdr., 2017/05/18 23:52:47]

Is it just for this node, or this node or any ancestor node?

[wkorman, 2017/05/19 00:37:03]

Just this node.

+  // Whether this node has a potentially running (i.e., irrespective
+  // of exact timeline) opacity animation.
   bool has_potential_opacity_animation;
+  // Whether this node has a currently running filter animation.
   bool is_currently_animating_filter;
+  // Whether this node has a currently running opacity animation.
   bool is_currently_animating_opacity;
-  // We need to track changes to effects on the compositor to compute damage
-  // rect.
+  // Whether this node's effect has been changed since last

[pdr., 2017/05/18 23:52:47]

Nit: since [the] last frame.

[wkorman, 2017/05/19 00:37:03]

Done.

+  // frame. Needed in order to compute damage rect.
   bool effect_changed;
   bool subtree_has_copy_request;
+  // The transform node index of the transform to apply to this effect
+  // node's content when rendering to a surface.
   int transform_id;
+  // The clip node index of the clip to apply to this effect node's
+  // content when rendering to a surface.
   int clip_id;
 
   // This is the id of the ancestor effect node that induces a
   // RenderSurfaceImpl.
   int target_id;
+  // The layer id of the mask layer, if any, to apply to this effect
+  // node's content when rendering to a surface.
+  // TODO(wkorman): It appears the only reads of this value are to

[wkorman, 2017/05/18 23:57:03]

I found the one reference of impact -- RenderSurfaceImpl::MaskLayer uses this to
look up the layer by id. I must have missed in my previous searching. Will
remove this TODO.

+  // determine whether the node has a mask for occlusion tracking
+  // purposes. Perhaps it can just be a bool?
   int mask_layer_id;
   int closest_ancestor_with_copy_request_id;
 
   bool operator==(const EffectNode& other) const;
 
   void AsValueInto(base::trace_event::TracedValue* value) const;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_EFFECT_NODE_H_