Refactor unreliable hit test code to avoid owning_layers

cc/trees/layer_tree_impl.cc

 // 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.
 
 #include "cc/trees/layer_tree_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1911 matching lines @@
       if (!state->closest_match || in_front_of_previous_candidate) {
         state->closest_distance = distance_to_intersection;
         state->closest_match = layer;
       }
     }
     UMA_HISTOGRAM_COUNTS("Compositing.LayerTreeImpl.FindClosestMatchingLayerUs",
                          timer.Elapsed().InMicroseconds());
   }
 }
 
-static bool IsScrollableOrDrawnScrollbarLayer(LayerImpl* layer) {
-  return layer->scrollable() ||
-         (layer->ToScrollbarLayer() &&
-          layer->is_drawn_render_surface_layer_list_member());
-}
-
-struct FindScrollingLayerOrScrollbarLayerFunctor {
+struct FindScrollingLayerOrDrawnScrollbarFunctor {
   bool operator()(LayerImpl* layer) const {
-    return IsScrollableOrDrawnScrollbarLayer(layer);
+    return layer->scrollable() || layer->IsDrawnScrollbar();
   }
 };
 
 LayerImpl*
-LayerTreeImpl::FindFirstScrollingLayerOrScrollbarLayerThatIsHitByPoint(
+LayerTreeImpl::FindFirstScrollingLayerOrDrawnScrollbarThatIsHitByPoint(
     const gfx::PointF& screen_space_point) {
   FindClosestMatchingLayerState state;
   LayerImpl* root_layer = layer_list_.empty() ? nullptr : layer_list_[0];
   FindClosestMatchingLayer(screen_space_point, root_layer,
-                           FindScrollingLayerOrScrollbarLayerFunctor(), &state);
+                           FindScrollingLayerOrDrawnScrollbarFunctor(), &state);
   return state.closest_match;
 }
 
 struct HitTestVisibleScrollableOrTouchableFunctor {
   bool operator()(LayerImpl* layer) const {
-    return layer->is_drawn_render_surface_layer_list_member() ||
-           IsScrollableOrDrawnScrollbarLayer(layer) ||
+    return layer->scrollable() ||

[pdr., 2017/02/27 21:40:05]

The original code was really checking the following:
if (layer->is_drawn_render_surface_layer_list_member()
  || layer->scrollable()
  || (layer->ToScrollbarLayer() &&
layer->is_drawn_render_surface_layer_list_member())
  || !layer->touch_event_handler_region().IsEmpty())

This checked is_drawn_render_surface_layer_list_member twice, and can be
refactored to only do it once.

+           layer->is_drawn_render_surface_layer_list_member() ||
            !layer->touch_event_handler_region().IsEmpty();
   }
 };
 
 LayerImpl* LayerTreeImpl::FindLayerThatIsHitByPoint(
     const gfx::PointF& screen_space_point) {
   if (layer_list_.empty())
     return NULL;
   bool update_lcd_text = false;
   if (!UpdateDrawProperties(update_lcd_text))
@@ skipping 150 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc