Add Plumbing for WM_DPICHANGED

ui/views/widget/desktop_aura/desktop_window_tree_host_win.h

 // 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_WIDGET_DESKTOP_AURA_DESKTOP_WINDOW_TREE_HOST_WIN_H_
 #define UI_VIEWS_WIDGET_DESKTOP_AURA_DESKTOP_WINDOW_TREE_HOST_WIN_H_
 
 #include "base/macros.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/views/views_export.h"
@@ skipping 178 matching lines @@
                            LRESULT* l_result) override;
   void HandleMenuLoop(bool in_menu_loop) override;
   bool PreHandleMSG(UINT message,
                     WPARAM w_param,
                     LPARAM l_param,
                     LRESULT* result) override;
   void PostHandleMSG(UINT message, WPARAM w_param, LPARAM l_param) override;
   bool HandleScrollEvent(const ui::ScrollEvent& event) override;
   void HandleWindowSizeChanging() override;
   void HandleWindowSizeChanged() override;
+  void HandleWindowScaleFactorChanged(float window_scale_factor) override;
 
   Widget* GetWidget();
   const Widget* GetWidget() const;
   HWND GetHWND() const;
 
  private:
   void SetWindowTransparency();
 
   // Returns true if a modal window is active in the current root window chain.
   bool IsModalWindowActive() const;
@@ skipping 56 matching lines @@
   // Indicates if current window will receive mouse events when should not
   // become activated.
   bool wants_mouse_events_when_inactive_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopWindowTreeHostWin);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_DESKTOP_AURA_DESKTOP_WINDOW_TREE_HOST_WIN_H_