Slightly refactor StickyPositionScrollingConstraints API and add documentation

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 312 matching lines @@
   web_constraint.top_offset = constraints.TopOffset();
   web_constraint.bottom_offset = constraints.BottomOffset();
   web_constraint.scroll_container_relative_sticky_box_rect =
       EnclosingIntRect(constraints.ScrollContainerRelativeStickyBoxRect());
   web_constraint.scroll_container_relative_containing_block_rect =
       EnclosingIntRect(
           constraints.ScrollContainerRelativeContainingBlockRect());
   // TODO(smcgruer): Until http://crbug.com/702229 is fixed, the nearest
   // sticky layers may not be composited and we may incorrectly end up with
   // invalid layer IDs.
-  LayoutBoxModelObject* sticky_box_shifting_ancestor =
-      constraints.NearestStickyBoxShiftingStickyBox();
+  PaintLayer* sticky_box_shifting_ancestor =
+      constraints.NearestStickyLayerShiftingStickyBox();
   if (sticky_box_shifting_ancestor &&
-      sticky_box_shifting_ancestor->Layer()->GetCompositedLayerMapping()) {
+      sticky_box_shifting_ancestor->GetCompositedLayerMapping()) {
     web_constraint.nearest_layer_shifting_sticky_box =
-        sticky_box_shifting_ancestor->Layer()
-            ->GetCompositedLayerMapping()
+        sticky_box_shifting_ancestor->GetCompositedLayerMapping()
             ->MainGraphicsLayer()
             ->PlatformLayer()
             ->Id();
   }
-  LayoutBoxModelObject* containing_block_shifting_ancestor =
-      constraints.NearestStickyBoxShiftingContainingBlock();
+  PaintLayer* containing_block_shifting_ancestor =
+      constraints.NearestStickyLayerShiftingContainingBlock();
   if (containing_block_shifting_ancestor &&
-      containing_block_shifting_ancestor->Layer()
-          ->GetCompositedLayerMapping()) {
+      containing_block_shifting_ancestor->GetCompositedLayerMapping()) {
     web_constraint.nearest_layer_shifting_containing_block =
-        containing_block_shifting_ancestor->Layer()
-            ->GetCompositedLayerMapping()
+        containing_block_shifting_ancestor->GetCompositedLayerMapping()
             ->MainGraphicsLayer()
             ->PlatformLayer()
             ->Id();
   }
 
   graphics_layer_->SetStickyPositionConstraint(web_constraint);
 }
 
 void CompositedLayerMapping::UpdateLayerBlendMode(const ComputedStyle& style) {
   SetBlendMode(style.BlendMode());
@@ skipping 3296 matching lines @@
   } else if (graphics_layer == decoration_outline_layer_.get()) {
     name = "Decoration Layer";
   } else {
     NOTREACHED();
   }
 
   return name;
 }
 
 }  // namespace blink