Remove scroll layer ids from scrollbar layers

cc/layers/painted_scrollbar_layer_unittest.cc

 // Copyright 2015 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/layers/painted_scrollbar_layer.h"
 
 #include "cc/animation/animation_host.h"
 #include "cc/test/fake_layer_tree_host.h"
 #include "cc/test/fake_layer_tree_host_client.h"
 #include "cc/test/fake_scrollbar.h"
@@ skipping 19 matching lines @@
 TEST(PaintedScrollbarLayerTest, NeedsPaint) {
   FakeLayerTreeHostClient fake_client_;
   TestTaskGraphRunner task_graph_runner_;
 
   auto animation_host = AnimationHost::CreateForTesting(ThreadInstance::MAIN);
   auto layer_tree_host = FakeLayerTreeHost::Create(
       &fake_client_, &task_graph_runner_, animation_host.get());
 
   MockScrollbar* scrollbar = new MockScrollbar();
   scoped_refptr<PaintedScrollbarLayer> scrollbar_layer =
-      PaintedScrollbarLayer::Create(std::unique_ptr<Scrollbar>(scrollbar), 1);
+      PaintedScrollbarLayer::Create(std::unique_ptr<Scrollbar>(scrollbar));
 
   scrollbar_layer->SetIsDrawable(true);
   scrollbar_layer->SetBounds(gfx::Size(100, 100));
 
   layer_tree_host->SetRootLayer(scrollbar_layer);
   EXPECT_EQ(scrollbar_layer->GetLayerTreeHostForTesting(),
             layer_tree_host.get());
   scrollbar_layer->SavePaintProperties();
 
   // Request no paint, but expect them to be painted because they have not
@@ skipping 23 matching lines @@
   EXPECT_CALL(*scrollbar, PaintPart(_, THUMB, _)).Times(0);
   EXPECT_CALL(*scrollbar, PaintPart(_, TRACK, _)).Times(1);
   scrollbar->set_needs_paint_thumb(false);
   scrollbar->set_needs_paint_track(true);
   scrollbar_layer->Update();
   Mock::VerifyAndClearExpectations(scrollbar);
 }
 
 }  // namespace
 }  // namespace cc