ui: Cleanup class/struct forward declarations

ui/views/linux_ui/linux_ui.h

 // Copyright 2013 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_LINUX_UI_LINUX_UI_H_
 #define UI_VIEWS_LINUX_UI_LINUX_UI_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 22 matching lines @@
 }
 
 namespace ui {
 class NativeTheme;
 }
 
 namespace views {
 class Border;
 class LabelButton;
 class LabelButtonBorder;
-class View;
 class WindowButtonOrderObserver;
 
 // Adapter class with targets to render like different toolkits. Set by any
 // project that wants to do linux desktop native rendering.
 //
 // TODO(erg): We're hardcoding GTK2, when we'll need to have backends for (at
 // minimum) GTK2 and GTK3. LinuxUI::instance() should actually be a very
 // complex method that pokes around with dlopen against a libuigtk2.so, a
 // liuigtk3.so, etc.
 class VIEWS_EXPORT LinuxUI : public ui::LinuxInputMethodContextFactory,
@@ skipping 102 matching lines @@
   // recalculated.
   virtual void UpdateDeviceScaleFactor() = 0;
 
   // Determines the device scale factor of the primary screen.
   virtual float GetDeviceScaleFactor() const = 0;
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_LINUX_UI_LINUX_UI_H_