Implement position: sticky updates on compositor

cc/layers/layer_impl.h

 // Copyright 2011 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_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 217 matching lines @@
     return use_parent_backface_visibility_;
   }
 
   void SetUseLocalTransformForBackfaceVisibility(bool use_local) {
     use_local_transform_for_backface_visibility_ = use_local;
   }
   bool use_local_transform_for_backface_visibility() const {
     return use_local_transform_for_backface_visibility_;
   }
 
+  void SetStickyPositionConstraint(
+      const LayerStickyPositionConstraint& constraint) {
+    sticky_position_constraint_ = constraint;
+  }
+  const LayerStickyPositionConstraint& sticky_position_constraint() const {
+    return sticky_position_constraint_;
+  }
+
   void SetShouldCheckBackfaceVisibility(bool should_check_backface_visibility) {
     should_check_backface_visibility_ = should_check_backface_visibility;
   }
   bool should_check_backface_visibility() const {
     return should_check_backface_visibility_;
   }
 
   bool ShowDebugBorders() const;
 
   // These invalidate the host's render surface layer list.  The caller
@@ skipping 314 matching lines @@
 
   // Denotes an area that is damaged and needs redraw. This is in the layer's
   // space.
   gfx::Rect damage_rect_;
 
   // Group of properties that need to be computed based on the layer tree
   // hierarchy before layers can be drawn.
   DrawProperties draw_properties_;
   PerformanceProperties<LayerImpl> performance_properties_;
 
+  LayerStickyPositionConstraint sticky_position_constraint_;

[ajuma, 2016/09/08 22:08:53]

Does LayerImpl need to know this? Is it enough for the transform tree to have
it? If you just need this for tests, it can go on LayerImplTestProperties
instead.

[flackr, 2016/09/20 17:08:12]

Done.

+
   std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
       owned_debug_info_;
   base::trace_event::ConvertableToTraceFormat* debug_info_;
   std::unique_ptr<RenderSurfaceImpl> render_surface_;
 
   bool scrolls_drawn_descendant_ : 1;
   bool has_will_change_transform_hint_ : 1;
   bool needs_push_properties_ : 1;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_