Implement position: sticky updates on compositor

cc/layers/layer_impl.cc

 // Copyright 2012 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/layers/layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 312 matching lines @@
   layer->offset_to_transform_parent_ = offset_to_transform_parent_;
   layer->main_thread_scrolling_reasons_ = main_thread_scrolling_reasons_;
   layer->user_scrollable_horizontal_ = user_scrollable_horizontal_;
   layer->user_scrollable_vertical_ = user_scrollable_vertical_;
   layer->should_flatten_transform_from_property_tree_ =
       should_flatten_transform_from_property_tree_;
   layer->masks_to_bounds_ = masks_to_bounds_;
   layer->contents_opaque_ = contents_opaque_;
   layer->may_contain_video_ = may_contain_video_;
   layer->use_parent_backface_visibility_ = use_parent_backface_visibility_;
+  layer->sticky_position_constraint_ = sticky_position_constraint_;
   layer->use_local_transform_for_backface_visibility_ =
       use_local_transform_for_backface_visibility_;
   layer->should_check_backface_visibility_ = should_check_backface_visibility_;
   layer->draws_content_ = draws_content_;
   layer->non_fast_scrollable_region_ = non_fast_scrollable_region_;
   layer->touch_event_handler_region_ = touch_event_handler_region_;
   layer->background_color_ = background_color_;
   layer->safe_opaque_background_color_ = safe_opaque_background_color_;
   layer->draw_blend_mode_ = draw_blend_mode_;
   layer->position_ = position_;
@@ skipping 776 matching lines @@
            .layer_transforms_should_scale_layer_contents) {
     return default_scale;
   }
 
   gfx::Vector2dF transform_scales = MathUtil::ComputeTransform2dScaleComponents(
       ScreenSpaceTransform(), default_scale);
   return std::max(transform_scales.x(), transform_scales.y());
 }
 
 }  // namespace cc