Store non-fast scrollable regions on ScrollNode

cc/trees/scroll_node.cc

 // Copyright 2016 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 "base/trace_event/trace_event_argument.h"
 #include "cc/base/math_util.h"
 #include "cc/input/main_thread_scrolling_reason.h"
 #include "cc/layers/layer.h"
 #include "cc/trees/element_id.h"
 #include "cc/trees/property_tree.h"
 #include "cc/trees/scroll_node.h"
 
 namespace cc {
 
 ScrollNode::ScrollNode()
     : id(ScrollTree::kInvalidNodeId),
       parent_id(ScrollTree::kInvalidNodeId),
       owning_layer_id(Layer::INVALID_ID),
       scrollable(false),
       main_thread_scrolling_reasons(
           MainThreadScrollingReason::kNotScrollingOnMain),
-      contains_non_fast_scrollable_region(false),
       max_scroll_offset_affected_by_page_scale(false),
       is_inner_viewport_scroll_layer(false),
       is_outer_viewport_scroll_layer(false),
       should_flatten(false),
       user_scrollable_horizontal(false),
       user_scrollable_vertical(false),
       transform_id(0) {}
 
 ScrollNode::ScrollNode(const ScrollNode& other) = default;
 
 bool ScrollNode::operator==(const ScrollNode& other) const {
   return id == other.id && parent_id == other.parent_id &&
          owning_layer_id == other.owning_layer_id &&
          scrollable == other.scrollable &&
          main_thread_scrolling_reasons == other.main_thread_scrolling_reasons &&
-         contains_non_fast_scrollable_region ==
-             other.contains_non_fast_scrollable_region &&
+         non_fast_scrollable_region == other.non_fast_scrollable_region &&

[wkorman, 2017/02/27 23:59:24]

And the SkRegion operator== logic is more complex than a bool:

https://cs.chromium.org/chromium/src/third_party/skia/src/core/SkRegion.cpp?t...

Again I think it's ok but worth commenting while reading.

          scroll_clip_layer_bounds == other.scroll_clip_layer_bounds &&
          bounds == other.bounds &&
          max_scroll_offset_affected_by_page_scale ==
              other.max_scroll_offset_affected_by_page_scale &&
          is_inner_viewport_scroll_layer ==
              other.is_inner_viewport_scroll_layer &&
          is_outer_viewport_scroll_layer ==
              other.is_outer_viewport_scroll_layer &&
          offset_to_transform_parent == other.offset_to_transform_parent &&
          should_flatten == other.should_flatten &&
@@ skipping 14 matching lines @@
                              offset_to_transform_parent, value);
   value->SetBoolean("should_flatten", should_flatten);
   value->SetBoolean("user_scrollable_horizontal", user_scrollable_horizontal);
   value->SetBoolean("user_scrollable_vertical", user_scrollable_vertical);
 
   element_id.AddToTracedValue(value);
   value->SetInteger("transform_id", transform_id);
 }
 
 }  // namespace cc