Overscroll and Elasticity for views::ScrollView

cc/trees/layer_tree_host_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_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <stddef.h>
 
 #include <bitset>
@@ skipping 182 matching lines @@
   void SetNeedsAnimateInput() override;
   bool IsCurrentlyScrollingViewport() const override;
   bool IsCurrentlyScrollingLayerAt(
       const gfx::Point& viewport_point,
       InputHandler::ScrollInputType type) const override;
   EventListenerProperties GetEventListenerProperties(
       EventListenerClass event_class) const override;
   bool DoTouchEventsBlockScrollAt(const gfx::Point& viewport_port) override;
   std::unique_ptr<SwapPromiseMonitor> CreateLatencyInfoSwapPromiseMonitor(
       ui::LatencyInfo* latency) override;
-  ScrollElasticityHelper* CreateScrollElasticityHelper() override;
+  ScrollElasticityHelper* CreateRootScrollElasticityHelper() override;
+  base::WeakPtr<ScrollElasticityHelper>
+  ScrollElasticityHelperForScrollingLayer() override;
   bool GetScrollOffsetForLayer(int layer_id,
                                gfx::ScrollOffset* offset) override;
   bool ScrollLayerTo(int layer_id, const gfx::ScrollOffset& offset) override;
 
   // TopControlsManagerClient implementation.
   float TopControlsHeight() const override;
   float BottomControlsHeight() const override;
   void SetCurrentTopControlsShownRatio(float offset) override;
   float CurrentTopControlsShownRatio() const override;
   void DidChangeTopControlsPosition() override;
@@ skipping 107 matching lines @@
   // Resets all of the trees to an empty state.
   void ResetTreesForTesting();
 
   size_t SourceAnimationFrameNumberForTesting() const;
 
   void RegisterScrollbarAnimationController(int scroll_layer_id);
   void UnregisterScrollbarAnimationController(int scroll_layer_id);
   ScrollbarAnimationController* ScrollbarAnimationControllerForId(
       int scroll_layer_id) const;
 
+  void RegisterScrollElasticityHelper(int scroll_layer_id);
+  void UnregisterScrollElasticityHelper(int scroll_layer_id);
+  ScrollElasticityHelper* ScrollElasticityHelperForId(int scroll_layer_id);
+
   DrawMode GetDrawMode() const;
 
   // Viewport size in draw space: this size is in physical pixels and is used
   // for draw properties, tilings, quads and render passes.
   gfx::Size DrawViewportSize() const;
 
   // Viewport rect in view space used for tiling prioritization.
   const gfx::Rect ViewportRectForTilePriority() const;
 
   // TileManagerClient implementation.
@@ skipping 402 matching lines @@
   bool did_lock_scrolling_layer_;
   bool wheel_scrolling_;
   bool scroll_affects_scroll_handler_;
   int scroll_layer_id_mouse_currently_over_;
 
   std::vector<std::unique_ptr<SwapPromise>>
       swap_promises_for_main_thread_scroll_update_;
 
   // An object to implement the ScrollElasticityHelper interface and
   // hold all state related to elasticity. May be NULL if never requested.
-  std::unique_ptr<ScrollElasticityHelper> scroll_elasticity_helper_;
+  std::unique_ptr<ScrollElasticityHelper> root_scroll_elasticity_helper_;
 
   bool tile_priorities_dirty_;
 
   const LayerTreeSettings settings_;
   LayerTreeDebugState debug_state_;
   bool visible_;
   ManagedMemoryPolicy cached_managed_memory_policy_;
 
   const bool is_synchronous_single_threaded_;
   TileManager tile_manager_;
@@ skipping 35 matching lines @@
   gfx::Rect viewport_damage_rect_;
 
   std::unique_ptr<AnimationHost> animation_host_;
   std::set<VideoFrameController*> video_frame_controllers_;
 
   // Map from scroll layer ID to scrollbar animation controller.
   // There is one animation controller per pair of overlay scrollbars.
   std::unordered_map<int, std::unique_ptr<ScrollbarAnimationController>>
       scrollbar_animation_controllers_;
 
+  // Map from scroll layer ID to elasticity helper.
+  std::unordered_map<int, std::unique_ptr<ScrollElasticityHelper>>
+      scroll_elasticity_helpers_;
+
   RenderingStatsInstrumentation* rendering_stats_instrumentation_;
   MicroBenchmarkControllerImpl micro_benchmark_controller_;
   std::unique_ptr<SynchronousTaskGraphRunner>
       single_thread_synchronous_task_graph_runner_;
 
   // Optional callback to notify of new tree activations.
   base::Closure tree_activation_callback_;
 
   SharedBitmapManager* shared_bitmap_manager_;
   gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager_;
@@ skipping 15 matching lines @@
 
   std::unique_ptr<PendingTreeDurationHistogramTimer>
       pending_tree_duration_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_