Unify the calculation of main thread offset of sticky element

cc/layers/layer_impl_test_properties.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_LAYERS_LAYER_IMPL_TEST_PROPERTIES_H_
 #define CC_LAYERS_LAYER_IMPL_TEST_PROPERTIES_H_
 
 #include <set>
 #include <vector>
 
@@ skipping 28 matching lines @@
   bool opacity_can_animate;
   bool subtree_has_copy_request;
   int sorting_context_id;
   float opacity;
   FilterOperations filters;
   FilterOperations background_filters;
   gfx::PointF filters_origin;
   SkBlendMode blend_mode;
   LayerPositionConstraint position_constraint;
   LayerStickyPositionConstraint sticky_position_constraint;
+  gfx::Size offset_for_sticky_position_from_main_thread;
   gfx::Point3F transform_origin;
   gfx::Transform transform;
   LayerImpl* scroll_parent;
   std::unique_ptr<std::set<LayerImpl*>> scroll_children;
   LayerImpl* clip_parent;
   std::unique_ptr<std::set<LayerImpl*>> clip_children;
   std::vector<std::unique_ptr<CopyOutputRequest>> copy_requests;
   LayerImplList children;
   LayerImpl* mask_layer;
   LayerImpl* parent;
   bool user_scrollable_horizontal = true;
   bool user_scrollable_vertical = true;
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_TEST_PROPERTIES_H_