Remove indirection: setup scrollbar scroll layers in the scrollbar constructor

cc/blink/web_scrollbar_layer_impl.cc

 // Copyright 2014 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/blink/web_scrollbar_layer_impl.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "cc/blink/scrollbar_impl.h"
@@ skipping 16 matching lines @@
                                                         : cc::VERTICAL;
 }
 
 }  // namespace
 
 namespace cc_blink {
 
 WebScrollbarLayerImpl::WebScrollbarLayerImpl(
     std::unique_ptr<blink::WebScrollbar> scrollbar,
     blink::WebScrollbarThemePainter painter,
-    std::unique_ptr<blink::WebScrollbarThemeGeometry> geometry)
+    std::unique_ptr<blink::WebScrollbarThemeGeometry> geometry,
+    blink::WebLayer* scroll_layer)
     : layer_(new WebLayerImpl(PaintedScrollbarLayer::Create(
           base::MakeUnique<ScrollbarImpl>(std::move(scrollbar),
                                           painter,
                                           std::move(geometry)),
-          0))) {}
+          static_cast<WebLayerImpl*>(scroll_layer)->layer()->id()))) {}
 
 WebScrollbarLayerImpl::WebScrollbarLayerImpl(
     std::unique_ptr<blink::WebScrollbar> scrollbar,
     blink::WebScrollbarThemePainter painter,
     std::unique_ptr<blink::WebScrollbarThemeGeometry> geometry,
-    bool)
+    bool,

[bokan, 2017/03/06 14:36:34]

Whoops, this bool argument is used solely to pick this overload of the
constructor but isn't used. I added this by accident. Could you name this
argument |is_overlay| and merge it with the above constructor, picking which
ScrollbarLayer type to create based on this bool? (alternatively I can fix this
myself after you land this patch).

[pdr., 2017/03/06 19:00:24]

Sure, removed.

+    blink::WebLayer* scroll_layer)
     : layer_(new WebLayerImpl(PaintedOverlayScrollbarLayer::Create(
           base::MakeUnique<ScrollbarImpl>(std::move(scrollbar),
                                           painter,
                                           std::move(geometry)),
-          0))) {}
+          static_cast<WebLayerImpl*>(scroll_layer)->layer()->id()))) {}
 
 WebScrollbarLayerImpl::WebScrollbarLayerImpl(
     blink::WebScrollbar::Orientation orientation,
     int thumb_thickness,
     int track_start,
-    bool is_left_side_vertical_scrollbar)
-    : layer_(new WebLayerImpl(
-          SolidColorScrollbarLayer::Create(ConvertOrientation(orientation),
-                                           thumb_thickness,
-                                           track_start,
-                                           is_left_side_vertical_scrollbar,
-                                           0))) {}
+    bool is_left_side_vertical_scrollbar,
+    blink::WebLayer* scroll_layer)
+    : layer_(new WebLayerImpl(SolidColorScrollbarLayer::Create(
+          ConvertOrientation(orientation),
+          thumb_thickness,
+          track_start,
+          is_left_side_vertical_scrollbar,
+          static_cast<WebLayerImpl*>(scroll_layer)->layer()->id()))) {}
 
 WebScrollbarLayerImpl::~WebScrollbarLayerImpl() {
 }
 
 blink::WebLayer* WebScrollbarLayerImpl::layer() {
   return layer_.get();
 }
 
-void WebScrollbarLayerImpl::setScrollLayer(blink::WebLayer* layer) {
-  cc::Layer* scroll_layer =
-      layer ? static_cast<WebLayerImpl*>(layer)->layer() : 0;
-  layer_->layer()->ToScrollbarLayer()->SetScrollLayer(
-      scroll_layer ? scroll_layer->id() : cc::Layer::INVALID_ID);
-}
-
 }  // namespace cc_blink