Remove scroll_clip_layer dependency from LayerTreeImpl::ScrollableSize

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 1212 matching lines @@
 }
 
 const Region& LayerTreeImpl::UnoccludedScreenSpaceRegion() const {
   // If this assert triggers, then the render_surface_list_ is dirty, so the
   // unoccluded_screen_space_region_ is not valid anymore.
   DCHECK(!needs_update_draw_properties_);
   return unoccluded_screen_space_region_;
 }
 
 gfx::SizeF LayerTreeImpl::ScrollableSize() const {
-  LayerImpl* root_scroll_layer = OuterViewportScrollLayer()
-                                     ? OuterViewportScrollLayer()
-                                     : InnerViewportScrollLayer();
-  if (!root_scroll_layer)
+  LayerImpl* root_scroll_layer = nullptr;
+  LayerImpl* root_container_layer = nullptr;
+  if (OuterViewportScrollLayer()) {
+    root_scroll_layer = OuterViewportScrollLayer();
+    root_container_layer = OuterViewportContainerLayer();
+  } else if (InnerViewportScrollLayer()) {
+    root_scroll_layer = InnerViewportScrollLayer();
+    root_container_layer = InnerViewportContainerLayer();
+  }
+
+  if (!root_scroll_layer || !root_container_layer)
     return gfx::SizeF();
 
   gfx::SizeF content_size = root_scroll_layer->BoundsForScrolling();
-  gfx::SizeF viewport_size =
-      root_scroll_layer->scroll_clip_layer()->BoundsForScrolling();
-
-  content_size.SetToMax(viewport_size);
+  content_size.SetToMax(root_container_layer->BoundsForScrolling());
   return content_size;
 }
 
 LayerImpl* LayerTreeImpl::LayerById(int id) const {
   LayerImplMap::const_iterator iter = layer_id_map_.find(id);
   return iter != layer_id_map_.end() ? iter->second : nullptr;
 }
 
 void LayerTreeImpl::AddLayerShouldPushProperties(LayerImpl* layer) {
   layers_that_should_push_properties_.insert(layer);
@@ skipping 880 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