Remove use_parent_backface_visibility on Layer and LayerImpl.

These fields are only ever set for content layers such as canvas
and video. However, such uses don't make sense any more, because the
"parent" concept originally had to do with a parent layer, which is
no longer a concept in layer list mode.

Bug: 1008483

Change-Id: I053f9048e5a152f84c4df761f1b1500a5a0019c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2129893Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755365}

cc/layers/layer.cc

@@ -80,7 +80,6 @@ Layer::Inputs::Inputs(int layer_id)
       contents_opaque(false),
       is_drawable(false),
       double_sided(true),
-      use_parent_backface_visibility(false),
       is_scrollbar(false),
       has_will_change_transform_hint(false),
       background_color(0) {}
@@ -1253,14 +1252,6 @@ std::string Layer::ToString() const {
       effect_tree_index(), scroll_tree_index(), transform_tree_index());
 }
 
-void Layer::SetUseParentBackfaceVisibility(bool use) {
-  DCHECK(IsPropertyChangeAllowed());
-  if (inputs_.use_parent_backface_visibility == use)
-    return;
-  inputs_.use_parent_backface_visibility = use;
-  SetNeedsPushProperties();
-}
-
 void Layer::SetShouldCheckBackfaceVisibility(
     bool should_check_backface_visibility) {
   if (should_check_backface_visibility_ == should_check_backface_visibility)
@@ -1344,7 +1335,6 @@ void Layer::PushPropertiesTo(LayerImpl* layer) {
     layer->SetWheelEventHandlerRegion(Region());
   }
   layer->SetContentsOpaque(inputs_.contents_opaque);
-  layer->SetUseParentBackfaceVisibility(inputs_.use_parent_backface_visibility);
   layer->SetShouldCheckBackfaceVisibility(should_check_backface_visibility_);
 
   layer->UpdateScrollable();

cc/layers/layer.h

@@ -491,17 +491,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   void SetDoubleSided(bool double_sided);
   bool double_sided() const { return inputs_.double_sided; }
 
-  // Set or get if SetDoubleSided() for this layer should be ignored and
-  // inherited directly from this layer's parent instead. Used to attach this
-  // layer's backface visibility to the value of its parent.
-  //
-  // Note that should_check_backface_visibility() is the final computed value
-  // for back face visibility, which is only for internal use.
-  void SetUseParentBackfaceVisibility(bool use);
-  bool use_parent_backface_visibility() const {
-    return inputs_.use_parent_backface_visibility;
-  }
-
   // When true the layer may contribute to the compositor's output. When false,
   // it does not. This property does not apply to children of the layer, they
   // may contribute while this layer does not. The layer itself will determine
@@ -724,7 +713,7 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
 
   // Internal to property tree construction. Set if the layer should not be
   // shown when its back face is visible to the user. This is a derived value
-  // from SetDoubleSided() and SetUseParentBackfaceVisibility().
+  // from SetDoubleSided().
   void SetShouldCheckBackfaceVisibility(bool should_check_backface_visibility);
   bool should_check_backface_visibility() const {
     return should_check_backface_visibility_;
@@ -860,7 +849,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
     bool is_drawable : 1;
 
     bool double_sided : 1;
-    bool use_parent_backface_visibility : 1;
 
     // Indicates that this layer is a scrollbar.
     bool is_scrollbar : 1;

cc/layers/layer_impl.cc

@@ -55,7 +55,6 @@ LayerImpl::LayerImpl(LayerTreeImpl* tree_impl,
       layer_property_changed_from_property_trees_(false),
       may_contain_video_(false),
       contents_opaque_(false),
-      use_parent_backface_visibility_(false),
       should_check_backface_visibility_(false),
       draws_content_(false),
       contributes_to_drawn_render_surface_(false),
@@ -371,7 +370,6 @@ void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   layer->offset_to_transform_parent_ = offset_to_transform_parent_;
   layer->contents_opaque_ = contents_opaque_;
   layer->may_contain_video_ = may_contain_video_;
-  layer->use_parent_backface_visibility_ = use_parent_backface_visibility_;
   layer->should_check_backface_visibility_ = should_check_backface_visibility_;
   layer->draws_content_ = draws_content_;
   layer->hit_testable_ = hit_testable_;

cc/layers/layer_impl.h

@@ -184,13 +184,6 @@ class CC_EXPORT LayerImpl {
 
   bool Is3dSorted() const { return GetSortingContextId() != 0; }
 
-  void SetUseParentBackfaceVisibility(bool use) {
-    use_parent_backface_visibility_ = use;
-  }
-  bool use_parent_backface_visibility() const {
-    return use_parent_backface_visibility_;
-  }
-
   void SetShouldCheckBackfaceVisibility(bool should_check_backface_visibility) {
     should_check_backface_visibility_ = should_check_backface_visibility;
   }
@@ -489,7 +482,6 @@ class CC_EXPORT LayerImpl {
 
   bool may_contain_video_ : 1;
   bool contents_opaque_ : 1;
-  bool use_parent_backface_visibility_ : 1;
   bool should_check_backface_visibility_ : 1;
   bool draws_content_ : 1;
   bool contributes_to_drawn_render_surface_ : 1;

cc/trees/draw_property_utils.cc

@@ -365,9 +365,7 @@ void SetHasContributingLayerThatEscapesClip(int lca_clip_id,
 template <typename LayerType>
 int TransformTreeIndexForBackfaceVisibility(LayerType* layer,
                                             const TransformTree& tree) {
-  if (!layer->use_parent_backface_visibility() || !layer->has_transform_node())
-    return layer->transform_tree_index();
-  return tree.Node(layer->transform_tree_index())->parent_id;
+  return layer->transform_tree_index();
 }
 
 bool IsTargetSpaceTransformBackFaceVisible(

cc/trees/property_tree_builder.cc

@@ -634,19 +634,12 @@ void PropertyTreeBuilderContext::AddScrollNodeIfNeeded(
 }
 
 void SetBackfaceVisibilityTransform(Layer* layer, bool created_transform_node) {
-  if (layer->use_parent_backface_visibility()) {
-    DCHECK(layer->parent());
-    DCHECK(!layer->parent()->use_parent_backface_visibility());
-    layer->SetShouldCheckBackfaceVisibility(
-        layer->parent()->should_check_backface_visibility());
-  } else {
-    // A double-sided layer's backface can been shown when its visible.
-    // In addition, we need to check if (1) there might be a local 3D transform
-    // on the layer that might turn it to the backface, or (2) it is not drawn
-    // into a flattened space.
-    layer->SetShouldCheckBackfaceVisibility(!layer->double_sided() &&
-                                            created_transform_node);
-  }
+  // A double-sided layer's backface can been shown when its visible.
+  // In addition, we need to check if (1) there might be a local 3D transform
+  // on the layer that might turn it to the backface, or (2) it is not drawn
+  // into a flattened space.
+  layer->SetShouldCheckBackfaceVisibility(!layer->double_sided() &&
+                                          created_transform_node);
 }
 
 void SetSafeOpaqueBackgroundColor(const DataForRecursion& data_from_ancestor,

third_party/blink/renderer/platform/graphics/graphics_layer.cc

@@ -447,7 +447,6 @@ void GraphicsLayer::SetContentsTo(scoped_refptr<cc::Layer> layer,
   if (layer) {
     if (contents_layer_ != layer) {
       contents_layer_ = std::move(layer);
-      contents_layer_->SetUseParentBackfaceVisibility(true);
       // It is necessary to call SetDrawsContent() as soon as we receive the new
       // contents_layer, for the correctness of early exit conditions in
       // SetDrawsContent() and SetContentsVisible().