Refactor PaintArtifactCompositor::CcLayer() to use RootLayer()

with PaintArtifactCompositor::RootLayer. This is a very simple cleanup.

PaintArtifactCompositor: :CcLayer is no longer needed and can be replaced
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ie3a4c07f0a514fc96ad2692eb22d6e5b3e106b27
Reviewed-on: https://chromium-review.googlesource.com/1117710
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571024}

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

@@ -3052,7 +3052,7 @@ void LocalFrameView::PushPaintArtifactToCompositor(
             // ScrollingCoordinator.
             WrapWeakPersistent(page->GetScrollingCoordinator())));
     page->GetChromeClient().AttachRootLayer(
-        paint_artifact_compositor_->GetCcLayer(), &GetFrame());
+        paint_artifact_compositor_->RootLayer(), &GetFrame());
   }
 
   SCOPED_UMA_AND_UKM_TIMER("Blink.Compositing.UpdateTime",

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

@@ -67,11 +67,6 @@ class PLATFORM_EXPORT PaintArtifactCompositor final
   // The root layer of the tree managed by this object.
   cc::Layer* RootLayer() const { return root_layer_.get(); }
 
-  // Wraps RootLayer(), so that it can be attached as a child of another
-  // cc::Layer.
-  // TODO(danakj): Remove this, use RootLayer() directly.
-  cc::Layer* GetCcLayer() const { return root_layer_.get(); }
-
   // Returns extra information recorded during unit tests.
   // While not part of the normal output of this class, this provides a simple
   // way of locating the layers of interest, since there are still a slew of

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

@@ -98,8 +98,7 @@ class PaintArtifactCompositorTest : public testing::Test,
     settings.use_layer_lists = true;
     web_layer_tree_view_ =
         std::make_unique<WebLayerTreeViewWithLayerTreeFrameSink>(settings);
-    web_layer_tree_view_->SetRootLayer(
-        paint_artifact_compositor_->GetCcLayer());
+    web_layer_tree_view_->SetRootLayer(paint_artifact_compositor_->RootLayer());
   }
 
   void TearDown() override {