Correct for enclosing layers scroll position in sticky_data->main_thread_offset

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 741 matching lines @@
       // viewport bounds change, but do not unconditionally move by that delta
       // like fixed position nodes.
       if (scroll_ancestor->is_inner_viewport_scroll_layer) {
         data_for_children->property_trees->transform_tree
             .AddNodeAffectedByInnerViewportBoundsDelta(node->id);
       } else if (scroll_ancestor->is_outer_viewport_scroll_layer) {
         data_for_children->property_trees->transform_tree
             .AddNodeAffectedByOuterViewportBoundsDelta(node->id);
       }
     }
-    sticky_data->main_thread_offset =
-        layer->position().OffsetFromOrigin() -
-        sticky_data->constraints.parent_relative_sticky_box_offset
-            .OffsetFromOrigin();
+
+    // The sticky box offset calculated in CompositedLayerMapping must be
+    // adjusted for the enclosing layer's scroll position.
+    gfx::Point sticky_box_offset(
+        sticky_data->constraints.parent_relative_sticky_box_offset);
+    if (Parent(layer)->id() != scroll_ancestor->owning_layer_id) {
+      sticky_box_offset -= gfx::ScrollOffsetToFlooredVector2d(
+          data_for_children->property_trees->scroll_tree.current_scroll_offset(
+              scroll_ancestor->owning_layer_id));
+    }
+
+    sticky_data->main_thread_offset = layer->position().OffsetFromOrigin() -
+                                      sticky_box_offset.OffsetFromOrigin();
   }
 
   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 767 matching lines @@
     color = SkColorSetA(color, 255);
   BuildPropertyTreesTopLevelInternal(
       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->ResetCachedData();
 }
 
 }  // namespace cc