Remove LayerTreeHost::SetNonBlinkManagedRootLayer() and force_use_property_tree_builder_

Due to flash removal in M88, remove |force_use_property_tree_builder_| and related logic.

Bug: 925855
Change-Id: Ia9826e35ea3c3e70fb235fba916aeeeed7d95ed6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2449840Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Stefan Zager <szager@chromium.org>
Commit-Queue: jongdeok.kim <jongdeok.kim@navercorp.com>
Cr-Commit-Position: refs/heads/master@{#815003}

cc/trees/layer_tree_host.cc

@@ -477,7 +477,7 @@ void LayerTreeHost::UpdateDeferMainFrameUpdateInternal() {
 }
 
 bool LayerTreeHost::IsUsingLayerLists() const {
-  return settings_.use_layer_lists && !force_use_property_tree_builder_;
+  return settings_.use_layer_lists;
 }
 
 void LayerTreeHost::CommitComplete() {
@@ -1153,20 +1153,9 @@ void LayerTreeHost::SetRootLayer(scoped_refptr<Layer> root_layer) {
   // This flag is sticky until a new tree comes along.
   gpu_rasterization_histogram_recorded_ = false;
 
-  force_use_property_tree_builder_ = false;
-
   SetNeedsFullTreeSync();
 }
 
-void LayerTreeHost::SetNonBlinkManagedRootLayer(
-    scoped_refptr<Layer> root_layer) {
-  SetRootLayer(std::move(root_layer));
-
-  DCHECK(!root_layer || root_layer_->children().empty());
-  if (IsUsingLayerLists() && root_layer_)
-    force_use_property_tree_builder_ = true;
-}
-
 void LayerTreeHost::RegisterViewportPropertyIds(
     const ViewportPropertyIds& ids) {
   DCHECK(IsUsingLayerLists());

cc/trees/layer_tree_host.h

@@ -341,14 +341,6 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
   Layer* root_layer() { return root_layer_.get(); }
   const Layer* root_layer() const { return root_layer_.get(); }
 
-  // Sets the root layer which is not managed by blink, and we will initialize
-  // its paint properties using PropertyTreeBuilder. For ui::Compositor, because
-  // for now we always use PropertyTreeBulder, this function is equivalent to
-  // SetRootLayer().
-  // TODO(crbug.com/925855): This is temporary. Eventually we should let the
-  // caller inform blink about the layer and remove the function.
-  void SetNonBlinkManagedRootLayer(scoped_refptr<Layer> root_layer);
-
   struct ViewportPropertyIds {
     int overscroll_elasticity_transform = TransformTree::kInvalidNodeId;
     int page_scale_transform = TransformTree::kInvalidNodeId;
@@ -911,13 +903,6 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
   // for every layer during property tree building.
   bool has_copy_request_ = false;
 
-  // When settings_.use_layer_lists is true, paint properties are generated by
-  // blink and we don't use PropertyTreeBuilder, except that the root layer
-  // is set by SetNonBlinkManagedRootLayer().
-  // TODO(crbug.com/925855): Remove this field when removing
-  // SetNonBlinkManagedRootLayer().
-  bool force_use_property_tree_builder_ = false;
-
   MutatorHost* mutator_host_;
 
   std::vector<std::pair<PaintImage, base::OnceCallback<void(bool)>>>

content/renderer/render_widget_unittest.cc

@@ -639,7 +639,7 @@ class NotifySwapTimesRenderWidgetUnittest : public RenderWidgetUnittest {
     auto root_layer = cc::SolidColorLayer::Create();
     root_layer->SetBounds(gfx::Size(200, 100));
     root_layer->SetBackgroundColor(SK_ColorGREEN);
-    widget()->layer_tree_host()->SetNonBlinkManagedRootLayer(root_layer);
+    widget()->layer_tree_host()->SetRootLayer(root_layer);
 
     auto color_layer = cc::SolidColorLayer::Create();
     color_layer->SetBounds(gfx::Size(100, 100));

third_party/blink/renderer/core/exported/web_external_widget_impl.cc

@@ -221,7 +221,7 @@ void WebExternalWidgetImpl::DidOverscrollForTesting(
 }
 
 void WebExternalWidgetImpl::SetRootLayer(scoped_refptr<cc::Layer> layer) {
-  widget_base_->LayerTreeHost()->SetNonBlinkManagedRootLayer(layer);
+  widget_base_->LayerTreeHost()->SetRootLayer(layer);
 }
 
 void WebExternalWidgetImpl::RecordTimeToFirstActivePaint(