Unify the calculation of main thread offset of sticky element

cc/trees/property_tree_builder.cc

 // Copyright 2014 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.
 
 #include "cc/trees/property_tree_builder.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <set>
@@ skipping 58 matching lines @@
 
 static LayerStickyPositionConstraint StickyPositionConstraint(Layer* layer) {
   return layer->sticky_position_constraint();
 }
 
 static LayerStickyPositionConstraint StickyPositionConstraint(
     LayerImpl* layer) {
   return layer->test_properties()->sticky_position_constraint;
 }
 
+static gfx::Size OffsetForStickyPositionFromMainThread(Layer* layer) {
+  return layer->offset_for_sticky_position_from_main_thread();
+}
+
+static gfx::Size OffsetForStickyPositionFromMainThread(LayerImpl* layer) {
+  return layer->test_properties()->offset_for_sticky_position_from_main_thread;
+}
+
 static LayerImplList& Children(LayerImpl* layer) {
   return layer->test_properties()->children;
 }
 
 static const LayerList& Children(Layer* layer) {
   return layer->children();
 }
 
 static LayerImpl* ChildAt(LayerImpl* layer, int index) {
   return layer->test_properties()->children[index];
@@ skipping 444 matching lines @@
       // viewport bounds change, but do not unconditionally move by that delta
       // like fixed position nodes.
       if (scroll_ancestor->scrolls_inner_viewport) {
         data_for_children->property_trees->transform_tree
             .AddNodeAffectedByInnerViewportBoundsDelta(node->id);
       } else if (scroll_ancestor->scrolls_outer_viewport) {
         data_for_children->property_trees->transform_tree
             .AddNodeAffectedByOuterViewportBoundsDelta(node->id);
       }
     }
-    // TODO(smcgruer): Pass main thread sticky-shifting offsets of
-    // non-promoted ancestors, or promote all ancestor sticky elements.
-    // See http://crbug.com/702229
-    sticky_data->main_thread_offset =
-        layer->position().OffsetFromOrigin() -
-        sticky_data->constraints.parent_relative_sticky_box_offset
-            .OffsetFromOrigin();
-
     // Copy the ancestor nodes for later use. These layers are guaranteed to
     // have transform nodes at this point because they are our ancestors (so
     // have already been processed) and are sticky (so have transform nodes).
     int shifting_sticky_box_layer_id =
         sticky_data->constraints.nearest_layer_shifting_sticky_box;
     if (shifting_sticky_box_layer_id != Layer::INVALID_ID) {
       sticky_data->nearest_node_shifting_sticky_box =
           data_for_children->property_trees->transform_tree
               .FindNodeIndexFromOwningLayerId(shifting_sticky_box_layer_id);
       DCHECK(sticky_data->nearest_node_shifting_sticky_box !=
              TransformTree::kInvalidNodeId);
     }
     int shifting_containing_block_layer_id =
         sticky_data->constraints.nearest_layer_shifting_containing_block;
     if (shifting_containing_block_layer_id != Layer::INVALID_ID) {
       sticky_data->nearest_node_shifting_containing_block =
           data_for_children->property_trees->transform_tree
               .FindNodeIndexFromOwningLayerId(
                   shifting_containing_block_layer_id);
       DCHECK(sticky_data->nearest_node_shifting_containing_block !=
              TransformTree::kInvalidNodeId);
     }
+    node->offset_for_sticky_position_from_main_thread =
+        gfx::Vector2dF(OffsetForStickyPositionFromMainThread(layer).width(),
+                       OffsetForStickyPositionFromMainThread(layer).height());
   }
 
   node->needs_local_transform_update = true;
   data_from_ancestor.property_trees->transform_tree.UpdateTransforms(node->id);
 
   layer->set_offset_to_transform_parent(gfx::Vector2dF());
 
   // Flattening (if needed) will be handled by |node|.
   layer->set_should_flatten_transform_from_property_tree(false);
 
@@ skipping 819 matching lines @@
       root_layer, page_scale_layer, inner_viewport_scroll_layer,
       outer_viewport_scroll_layer, overscroll_elasticity_layer,
       elastic_overscroll, page_scale_factor, device_scale_factor, viewport,
       device_transform, property_trees, color);
   property_trees->effect_tree.CreateOrReuseRenderSurfaces(
       &render_surfaces, root_layer->layer_tree_impl());
   property_trees->ResetCachedData();
 }
 
 }  // namespace cc