[Refactor] Moved scrollbar creation and deletion to ScrollbarManager

third_party/WebKit/Source/core/paint/ScrollbarManager.cpp

 // Copyright 2016 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 "core/paint/ScrollbarManager.h"
 
+#include "core/frame/LocalFrame.h"
+#include "core/frame/LocalFrameView.h"
+#include "core/layout/LayoutBox.h"
+#include "core/layout/LayoutObject.h"
+#include "core/layout/LayoutScrollbar.h"
+#include "core/layout/LayoutTheme.h"
+#include "core/page/ChromeClient.h"
+#include "core/page/Page.h"
+#include "core/paint/PaintLayerScrollableArea.h"
+
 namespace blink {
 
 ScrollbarManager::ScrollbarManager(ScrollableArea& scrollable_area)
     : scrollable_area_(&scrollable_area),
       h_bar_is_attached_(0),
       v_bar_is_attached_(0) {}
 
 DEFINE_TRACE(ScrollbarManager) {
   visitor->Trace(scrollable_area_);
   visitor->Trace(h_bar_);
   visitor->Trace(v_bar_);
 }
 
 void ScrollbarManager::Dispose() {
   h_bar_is_attached_ = v_bar_is_attached_ = 0;
   DestroyScrollbar(kHorizontalScrollbar);
   DestroyScrollbar(kVerticalScrollbar);
 }
 
+Scrollbar* ScrollbarManager::CreateScrollbar(ScrollbarOrientation orientation) {
+  DCHECK(scrollable_area_->GetLayoutBox());
+  DCHECK(orientation == kHorizontalScrollbar ? !h_bar_is_attached_
+                                             : !v_bar_is_attached_);
+  LayoutObject* layout_object_for_style =
+      scrollable_area_->LayoutObjectForScrollbarStyle();
+
+  Scrollbar* scrollbar = nullptr;
+  if (layout_object_for_style &&
+      layout_object_for_style->HasCustomScrollbarStyle()) {
+    DCHECK(!layout_object_for_style->IsLayoutView());
+    scrollbar = LayoutScrollbar::CreateCustomScrollbar(
+        scrollable_area_.Get(), orientation,
+        ToElement(layout_object_for_style->GetNode()));
+  } else {
+    ScrollbarControlSize scrollbar_size = kRegularScrollbar;
+
+    if (layout_object_for_style &&
+        layout_object_for_style->StyleRef().HasAppearance() &&
+        scrollable_area_->IsPaintLayerScrollableArea()) {
+      scrollbar_size = LayoutTheme::GetTheme().ScrollbarControlSizeForPart(
+          layout_object_for_style->StyleRef().Appearance());
+    }
+
+    scrollbar =
+        Scrollbar::Create(scrollable_area_.Get(), orientation, scrollbar_size,
+                          &scrollable_area_->GetLayoutBox()
+                               ->GetFrame()
+                               ->GetPage()
+                               ->GetChromeClient());
+  }
+
+  scrollable_area_->GetLayoutBox()->GetDocument().View()->AddScrollbar(
+      scrollbar);
+
+  return scrollbar;
+}
+
+void ScrollbarManager::DestroyScrollbar(ScrollbarOrientation orientation) {
+  Member<Scrollbar>& scrollbar =
+      orientation == kHorizontalScrollbar ? h_bar_ : v_bar_;
+  DCHECK(orientation == kHorizontalScrollbar ? !h_bar_is_attached_
+                                             : !v_bar_is_attached_);
+  if (!scrollbar)
+    return;
+
+  scrollable_area_->WillRemoveScrollbar(*scrollbar, orientation);
+
+  scrollable_area_->GetLayoutBox()->GetDocument().View()->RemoveScrollbar(
+      scrollbar);
+
+  scrollbar->DisconnectFromScrollableArea();
+  scrollbar = nullptr;
+}
+
 }  // namespace blink