Implement position: sticky updates on compositor

cc/layers/layer_sticky_position_constraint.h

+// Copyright 2013 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_STICKY_POSITION_CONSTRAINT_H_
+#define CC_LAYERS_LAYER_STICKY_POSITION_CONSTRAINT_H_
+
+#include "cc/base/cc_export.h"
+
+#include "ui/gfx/geometry/rect.h"
+
+namespace cc {
+
+struct CC_EXPORT LayerStickyPositionConstraint {
+  LayerStickyPositionConstraint();
+  LayerStickyPositionConstraint(const LayerStickyPositionConstraint& other);
+
+  bool is_sticky : 1;
+  bool is_anchored_left : 1;
+  bool is_anchored_right : 1;
+  bool is_anchored_top : 1;
+  bool is_anchored_bottom : 1;
+  float left_offset;
+  float right_offset;
+  float top_offset;
+  float bottom_offset;
+  gfx::Rect absolute_sticky_box_rect;
+  gfx::Rect absolute_containing_block_rect;

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

Please add a comment explaining what the offsets and rects represent.

[flackr, 2016/09/20 17:08:13]

Done.

+
+  bool operator==(const LayerStickyPositionConstraint&) const;
+  bool operator!=(const LayerStickyPositionConstraint&) const;
+};
+
+}  // namespace cc
+
+#endif  // CC_LAYERS_LAYER_STICKY_POSITION_CONSTRAINT_H_