Scrollbar fade animation broken on Android regression resolved.

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 679 matching lines @@
 
   void ScrollAnimationAbort(LayerImpl* layer_impl);
 
   bool ScrollAnimationUpdateTarget(ScrollNode* scroll_node,
                                    const gfx::Vector2dF& scroll_delta,
                                    base::TimeDelta delayed_by);
 
   void SetCompositorContextVisibility(bool is_visible);
   void SetWorkerContextVisibility(bool is_visible);
 
+  // Cache & restore variables that get reset in ClearCurrentlyScrollingLayer.
+  // This is used to restore the variables' values in a scrollBegin event
+  // that is in inertial phase (a fling) to lach the event to its corresponding

[tdresser, 2016/10/19 15:28:04]

lach -> latch.

[sahel, 2016/10/25 15:34:14]

Done.

+  // scroll.

[tdresser, 2016/10/19 15:28:04]

scroll -> scroller.

[sahel, 2016/10/25 15:34:14]

Done.

+  void CacheScrollingVariablesState();

[tdresser, 2016/10/19 15:28:04]

Can we come up with a more specific name than "ScrollingVariables"? There are
other scrolling related variables that aren't included here.

[sahel, 2016/10/25 15:34:14]

You are right, but I couldn't come up with a better name, because the cached
variables are not related to each other. I would appreciate any ideas/help here.

[bokan, 2016/10/25 17:29:21]

How about CacheScrollStateForFling (FlingContinuation? EnsuingFling?
SubsequentFling?) and calling the class ScrollStateForFling?

[sahel, 2016/10/26 14:11:43]

Done.

+  void RestoreCachedScrollingVariablesState();
+
   using UIResourceMap = std::unordered_map<UIResourceId, UIResourceData>;
   UIResourceMap ui_resource_map_;
 
   // Resources that were evicted by EvictAllUIResources. Resources are removed
   // from this when they are touched by a create or destroy from the UI resource
   // request queue.
   std::set<UIResourceId> evicted_ui_resources_;
 
   CompositorFrameSink* compositor_frame_sink_;
 
@@ skipping 25 matching lines @@
 
   // In impl-side painting mode, tree with possibly incomplete rasterized
   // content. May be promoted to active by ActivatePendingTree().
   std::unique_ptr<LayerTreeImpl> pending_tree_;
 
   // In impl-side painting mode, inert tree with layers that can be recycled
   // by the next sync from the main thread.
   std::unique_ptr<LayerTreeImpl> recycle_tree_;
 
   InputHandlerClient* input_handler_client_;
   bool did_lock_scrolling_layer_;

[tdresser, 2016/10/19 15:28:04]

Can we put these in the struct here as well?

[sahel, 2016/10/25 15:34:14]

I am not sure if it's a good idea to do so, because they are not logically
related to each other, and they are accessed in different places/functions.

[bokan, 2016/10/25 17:29:21]

Yah, wheel_scrolling_ is set in ScrollBeginImpl which we call on a fling and the
others are set/reset in mouse moves/up/down so I don't think they're part of
"FlingState"

   bool wheel_scrolling_;
   bool scroll_affects_scroll_handler_;
   int scroll_layer_id_when_mouse_over_scrollbar_;
   int captured_scrollbar_layer_id_;
 
   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.
@@ skipping 81 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_