Do not ignore SolidColorScrollbarLayer's scroll_layer_id ctor argument

cc/trees/layer_tree_host_unittest_damage.cc

 // Copyright 2012 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.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/location.h"
 #include "base/time/time.h"
@@ skipping 336 matching lines @@
     scroll_clip_layer->SetBounds(
         gfx::Size(content_layer_->bounds().width() - 30,
                   content_layer_->bounds().height() - 50));
     scroll_clip_layer->AddChild(content_layer_);
     root_layer->AddChild(scroll_clip_layer);
 
     scoped_refptr<Layer> scrollbar_layer =
         FakePaintedScrollbarLayer::Create(false, true, content_layer_->id());
     scrollbar_layer->SetPosition(gfx::PointF(300.f, 300.f));
     scrollbar_layer->SetBounds(gfx::Size(10, 100));
-    scrollbar_layer->ToScrollbarLayer()->SetScrollLayer(content_layer_->id());
     root_layer->AddChild(scrollbar_layer);
 
     gfx::RectF content_rect(content_layer_->position(),
                             gfx::SizeF(content_layer_->bounds()));
     gfx::RectF scrollbar_rect(scrollbar_layer->position(),
                               gfx::SizeF(scrollbar_layer->bounds()));
     EXPECT_FALSE(content_rect.Intersects(scrollbar_rect));
 
     LayerTreeHostDamageTest::SetupTree();
     client_.set_bounds(root_layer->bounds());
@@ skipping 158 matching lines @@
 
   void AfterTest() override { EXPECT_EQ(3, num_draws_); }
 
   int num_draws_;
 };
 
 MULTI_THREAD_TEST_F(LayerTreeHostDamageTestScrollbarCommitDoesNoDamage);
 
 }  // namespace
 }  // namespace cc