cc: Construct the RSLL without using layer hierarchy

cc/trees/layer_tree_host_impl_unittest.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 947 matching lines @@
   scroll->SetBounds(scroll_content_size);
   scroll->SetScrollClipLayer(clip->id());
   scroll->SetDrawsContent(true);
 
   std::unique_ptr<SolidColorScrollbarLayerImpl> scrollbar =
       SolidColorScrollbarLayerImpl::Create(layer_tree_impl, 4, VERTICAL, 10, 0,
                                            false, true);
   scrollbar->SetBounds(scrollbar_size);
   scrollbar->SetPosition(gfx::PointF(345, 0));
   scrollbar->SetScrollLayerId(scroll->id());
-  scrollbar->set_layer_or_descendant_is_drawn(true);
   scrollbar->SetDrawsContent(true);
+  scrollbar->SetOpacity(1.f);
 
   std::unique_ptr<LayerImpl> squash1 = LayerImpl::Create(layer_tree_impl, 5);
   squash1->SetBounds(gfx::Size(140, 300));
   squash1->SetPosition(gfx::PointF(220, 0));
   squash1->SetDrawsContent(true);
 
   std::unique_ptr<LayerImpl> squash2 = LayerImpl::Create(layer_tree_impl, 6);
   squash2->SetBounds(gfx::Size(140, 300));
   squash2->SetPosition(gfx::PointF(220, 300));
   squash2->SetDrawsContent(true);
@@ skipping 9693 matching lines @@
     // There should not be any jitter measured till we hit the fixed point hits
     // threshold.
     float expected_jitter =
         (i == pending_tree->kFixedPointHitsThreshold) ? 500 : 0;
     EXPECT_EQ(jitter, expected_jitter);
   }
 }
 
 }  // namespace
 }  // namespace cc