Compute if a layer is drawn without LayerTree hierarchy

cc/trees/layer_tree_host_pixeltest_readback.cc

Index: cc/trees/layer_tree_host_pixeltest_readback.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_readback.cc b/cc/trees/layer_tree_host_pixeltest_readback.cc
index 6f2143982a2e662fa6b7f67be454faee71b0d11e..e4c7b6e3565222213b40864781a4819eeeb75b48 100644
--- a/cc/trees/layer_tree_host_pixeltest_readback.cc
+++ b/cc/trees/layer_tree_host_pixeltest_readback.cc
@@ -263,7 +263,8 @@ TEST_P(LayerTreeHostReadbackPixelTest, ReadbackHiddenSubtree) {
 
   scoped_refptr<SolidColorLayer> hidden_target =
       CreateSolidColorLayer(gfx::Rect(200, 200), SK_ColorGREEN);
-  hidden_target->SetHideLayerAndSubtree(true);
+  // Set opacity to 0 to hide subtree.
+  hidden_target->SetOpacity(0.f);
   background->AddChild(hidden_target);
 
   scoped_refptr<SolidColorLayer> blue =
@@ -283,7 +284,8 @@ TEST_P(LayerTreeHostReadbackPixelTest,
 
   scoped_refptr<SolidColorLayer> hidden_target =
       CreateSolidColorLayer(gfx::Rect(200, 200), SK_ColorGREEN);
-  hidden_target->SetHideLayerAndSubtree(true);
+  // Set opacity to 0 to hide subtree.
+  hidden_target->SetOpacity(0.f);
   background->AddChild(hidden_target);
 
   scoped_refptr<SolidColorLayer> blue =