[CompositeAfterPaint] Let cc know the viewport page scale transform node

Bug: 726066, 909750
Change-Id: I12242ad3facdc7e8877833d2c436e383f2c9530f
Reviewed-on: https://chromium-review.googlesource.com/c/1352322
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612030}

cc/trees/layer_tree_host.cc

@@ -1067,6 +1067,13 @@ void LayerTreeHost::RegisterViewportLayers(const ViewportLayers& layers) {
   viewport_layers_.outer_viewport_scroll = layers.outer_viewport_scroll;
 }
 
+void LayerTreeHost::RegisterViewportPropertyIds(
+    const ViewportPropertyIds& ids) {
+  DCHECK(!viewport_layers_.inner_viewport_scroll);
+  DCHECK(IsUsingLayerLists());
+  viewport_property_ids_ = ids;
+}
+
 void LayerTreeHost::RegisterSelection(const LayerSelection& selection) {
   if (selection_ == selection)
     return;
@@ -1489,6 +1496,8 @@ void LayerTreeHost::PushLayerTreePropertiesTo(LayerTreeImpl* tree_impl) {
     tree_impl->ClearViewportLayers();
   }
 
+  tree_impl->set_viewport_property_ids(viewport_property_ids_);
+
   tree_impl->RegisterSelection(selection_);
 
   tree_impl->PushPageScaleFromMainThread(

cc/trees/layer_tree_host.h

@@ -333,6 +333,16 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
     return viewport_layers_.outer_viewport_scroll.get();
   }
 
+  // Counterpart of ViewportLayers for CompositeAfterPaint which doesn't create
+  // viewport layers.
+  struct ViewportPropertyIds {
+    int page_scale_transform = TransformTree::kInvalidNodeId;
+    // TODO(crbug.com/909750): Switch other usages of viewport layers to
+    // property ids for CompositeAfterPaint.
+  };
+
+  void RegisterViewportPropertyIds(const ViewportPropertyIds&);
+
   // Sets or gets the position of touch handles for a text selection. These are
   // submitted to the display compositor along with the Layer tree's contents
   // allowing it to present the selection handles. This is done because the
@@ -733,6 +743,8 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
   scoped_refptr<Layer> root_layer_;
 
   ViewportLayers viewport_layers_;
+  // For CompositeAfterPaint.
+  ViewportPropertyIds viewport_property_ids_;
 
   float top_controls_height_ = 0.f;
   float top_controls_shown_ratio_ = 0.f;

cc/trees/layer_tree_impl.cc

@@ -842,8 +842,12 @@ void LayerTreeImpl::UpdateTransformAnimation(ElementId element_id,
 
 TransformNode* LayerTreeImpl::PageScaleTransformNode() {
   auto* page_scale = PageScaleLayer();
-  if (!page_scale)
-    return nullptr;
+  if (!page_scale) {
+    // TODO(crbug.com/909750): Check all other callers of PageScaleLayer() and
+    // switch to viewport_property_ids_.page_scale_transform if needed.
+    return property_trees()->transform_tree.Node(
+        viewport_property_ids_.page_scale_transform);
+  }
 
   return property_trees()->transform_tree.Node(
       page_scale->transform_tree_index());
@@ -858,8 +862,8 @@ void LayerTreeImpl::UpdatePageScaleNode() {
   // When the page scale layer is also the root layer (this happens in the UI
   // compositor), the node should also store the combined scale factor and not
   // just the page scale factor.
-  // TODO(bokan): Need to implement this behavior for
-  // BlinkGeneratedPropertyTrees. i.e. (no page scale layer).
+  // TODO(crbug.com/909750): Implement this behavior without PageScaleLayer,
+  // e.g. when we switch the UI compositor to create property trees.
   float device_scale_factor_for_page_scale_layer = 1.f;
   gfx::Transform device_transform_for_page_scale_layer;
   if (IsRootLayer(PageScaleLayer())) {

cc/trees/layer_tree_impl.h

@@ -286,6 +286,11 @@ class CC_EXPORT LayerTreeImpl {
         const_cast<const LayerTreeImpl*>(this)->OuterViewportScrollNode());
   }
 
+  void set_viewport_property_ids(
+      const LayerTreeHost::ViewportPropertyIds& ids) {
+    viewport_property_ids_ = ids;
+  }
+
   void ApplySentScrollAndScaleDeltasFromAbortedCommit();
 
   SkColor background_color() const { return background_color_; }
@@ -648,6 +653,7 @@ class CC_EXPORT LayerTreeImpl {
   int last_scrolled_scroll_node_index_;
 
   ViewportLayerIds viewport_layer_ids_;
+  LayerTreeHost::ViewportPropertyIds viewport_property_ids_;
 
   LayerSelection selection_;
 

third_party/blink/renderer/core/frame/local_frame_view.cc

@@ -2935,7 +2935,7 @@ void LocalFrameView::PushPaintArtifactToCompositor(
 
   paint_artifact_compositor_->Update(
       paint_controller_->GetPaintArtifactShared(), composited_element_ids,
-      frame_->GetPage()->GetVisualViewport().GetPageScaleNode());
+      page->GetVisualViewport().GetPageScaleNode());
 }
 
 std::unique_ptr<JSONObject> LocalFrameView::CompositedLayersAsJSON(

third_party/blink/renderer/platform/graphics/compositing/paint_artifact_compositor.cc

@@ -780,13 +780,14 @@ void PaintArtifactCompositor::Update(
   Vector<PendingLayer, 0> pending_layers;
   CollectPendingLayers(*paint_artifact, pending_layers);
 
-  // The page scale layer would create this below but we need to use the
-  // special EnsureCompositorPageScaleTransformNode method since the transform
-  // created in a different way so we call it here.
+  cc::LayerTreeHost::ViewportPropertyIds viewport_property_ids;
   if (viewport_scale_node) {
-    property_tree_manager.EnsureCompositorPageScaleTransformNode(
-        viewport_scale_node);
+    viewport_property_ids.page_scale_transform =
+        property_tree_manager.EnsureCompositorPageScaleTransformNode(
+            viewport_scale_node);
   }
+  if (RuntimeEnabledFeatures::SlimmingPaintV2Enabled())
+    host->RegisterViewportPropertyIds(viewport_property_ids);
 
   Vector<std::unique_ptr<ContentLayerClientImpl>> new_content_layer_clients;
   new_content_layer_clients.ReserveCapacity(pending_layers.size());

third_party/blink/renderer/platform/graphics/compositing/property_tree_manager.cc

@@ -290,7 +290,7 @@ int PropertyTreeManager::EnsureCompositorTransformNode(
   return id;
 }
 
-void PropertyTreeManager::EnsureCompositorPageScaleTransformNode(
+int PropertyTreeManager::EnsureCompositorPageScaleTransformNode(
     const TransformPaintPropertyNode* node) {
   int id = EnsureCompositorTransformNode(node);
   DCHECK(GetTransformTree().Node(id));
@@ -303,6 +303,8 @@ void PropertyTreeManager::EnsureCompositorPageScaleTransformNode(
   compositor_node.post_local.matrix() = compositor_node.local.matrix();
   compositor_node.pre_local.matrix().setIdentity();
   compositor_node.local.matrix().setIdentity();
+
+  return id;
 }
 
 int PropertyTreeManager::EnsureCompositorClipNode(

third_party/blink/renderer/platform/graphics/compositing/property_tree_manager.h

@@ -100,8 +100,7 @@ class PropertyTreeManager {
   int EnsureCompositorScrollNode(
       const TransformPaintPropertyNode* scroll_offset_translation);
 
-  void EnsureCompositorPageScaleTransformNode(
-      const TransformPaintPropertyNode*);
+  int EnsureCompositorPageScaleTransformNode(const TransformPaintPropertyNode*);
 
   // This function is expected to be invoked right before emitting each layer.
   // It keeps track of the nesting of clip and effects, output a composited