Update from https://crrev.com/306655

cc/trees/layer_tree_host_pixeltest_masks.cc

Index: cc/trees/layer_tree_host_pixeltest_masks.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_masks.cc b/cc/trees/layer_tree_host_pixeltest_masks.cc
index c49491493765143d76611975b1c83e8b4849ef1d..1235e15fdfa52fa218c355fdd4fbea3d862c21e6 100644
--- a/cc/trees/layer_tree_host_pixeltest_masks.cc
+++ b/cc/trees/layer_tree_host_pixeltest_masks.cc
@@ -47,6 +47,13 @@ class MaskContentLayerClient : public ContentLayerClient {
     }
   }
 
+  scoped_refptr<DisplayItemList> PaintContentsToDisplayList(
+      const gfx::Rect& clip,
+      GraphicsContextStatus gc_status) override {
+    NOTIMPLEMENTED();
+    return DisplayItemList::Create();
+  }
+
  private:
   gfx::Size bounds_;
 };