[BlinkGenPropertyTrees] Remove more cc::Layer hierarchy changes

This patch is a followup to https://crrev.com/605470 and removes more
cc::Layer hierarchy modifications from GraphicsLayers. We rely on
cc::Layers being updated in PaintArtifactCompositor (PAC).

Bug: 898668
Change-Id: I021119d3ddd3314bba03614f2fb4ce9f07ea62eb
Reviewed-on: https://chromium-review.googlesource.com/c/1337288Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608508}

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

@@ -241,7 +241,12 @@ void GraphicsLayer::RemoveFromParent() {
     SetParent(nullptr);
   }
 
-  CcLayer()->RemoveFromParent();
+  // When using layer lists, cc::Layers are created and removed in
+  // PaintArtifactCompositor.
+  if (!RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled() &&
+      !RuntimeEnabledFeatures::SlimmingPaintV2Enabled()) {
+    CcLayer()->RemoveFromParent();
+  }
 }
 
 void GraphicsLayer::SetOffsetFromLayoutObject(const IntSize& offset) {
@@ -519,7 +524,10 @@ void GraphicsLayer::SetupContentsLayer(cc::Layer* contents_layer) {
 
   // Insert the content layer first. Video elements require this, because they
   // have shadow content that must display in front of the video.
-  CcLayer()->InsertChild(contents_layer_, 0);
+  if (!RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled() &&
+      !RuntimeEnabledFeatures::SlimmingPaintV2Enabled()) {
+    CcLayer()->InsertChild(contents_layer_, 0);
+  }
   cc::PictureLayer* border_cc_layer =
       contents_clipping_mask_layer_ ? contents_clipping_mask_layer_->CcLayer()
                                     : nullptr;