ui: Cleanup class/struct forward declarations

ui/views/controls/scrollbar/native_scroll_bar.h

Index: ui/views/controls/scrollbar/native_scroll_bar.h
diff --git a/ui/views/controls/scrollbar/native_scroll_bar.h b/ui/views/controls/scrollbar/native_scroll_bar.h
deleted file mode 100644
index c94089514c3fdedc41ffc4a84ba7370fd2378658..0000000000000000000000000000000000000000
--- a/ui/views/controls/scrollbar/native_scroll_bar.h
+++ /dev/null
@@ -1,74 +0,0 @@
-// Copyright (c) 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.
-
-#ifndef UI_VIEWS_CONTROLS_SCROLLBAR_NATIVE_SCROLL_BAR_H_
-#define UI_VIEWS_CONTROLS_SCROLLBAR_NATIVE_SCROLL_BAR_H_
-
-#include <string>
-
-#include "base/compiler_specific.h"
-#include "base/gtest_prod_util.h"
-#include "base/macros.h"
-#include "ui/views/controls/scrollbar/scroll_bar.h"
-#include "ui/views/view.h"
-
-namespace ui {
-class NativeTheme;
-}
-
-namespace views {
-namespace test {
-class ScrollViewTestApi;
-}
-
-class NativeScrollBarWrapper;
-
-// The NativeScrollBar class is a scrollbar that uses platform's
-// native control.
-class VIEWS_EXPORT NativeScrollBar : public ScrollBar {
- public:
-  // The scroll-bar's class name.
-  static const char kViewClassName[];
-
-  // Create new scrollbar, either horizontal or vertical.
-  explicit NativeScrollBar(bool is_horiz);
-  ~NativeScrollBar() override;
-
-  // Return the system sizes.
-  static int GetHorizontalScrollBarHeight(const ui::NativeTheme* theme);
-  static int GetVerticalScrollBarWidth(const ui::NativeTheme* theme);
-
- private:
-  friend class NativeScrollBarTest;
-  friend class test::ScrollViewTestApi;
-  FRIEND_TEST_ALL_PREFIXES(NativeScrollBarTest, Scrolling);
-
-  // Overridden from View.
-  gfx::Size GetPreferredSize() const override;
-  void Layout() override;
-  void ViewHierarchyChanged(
-      const ViewHierarchyChangedDetails& details) override;
-  const char* GetClassName() const override;
-
-  // Overrideen from View for keyboard UI purpose.
-  bool OnKeyPressed(const ui::KeyEvent& event) override;
-  bool OnMouseWheel(const ui::MouseWheelEvent& e) override;
-
-  // Overridden from ui::EventHandler.
-  void OnGestureEvent(ui::GestureEvent* event) override;
-
-  // Overridden from ScrollBar.
-  void Update(int viewport_size, int content_size, int current_pos) override;
-  int GetPosition() const override;
-  int GetLayoutSize() const override;
-
-  // init border
-  NativeScrollBarWrapper* native_wrapper_;
-
-  DISALLOW_COPY_AND_ASSIGN(NativeScrollBar);
-};
-
-}  // namespace views
-
-#endif  // UI_VIEWS_CONTROLS_SCROLLBAR_NATIVE_SCROLL_BAR_H_