Disable win/ash on high dpi screens

ui/gfx/win/dpi.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_GFX_DPI_WIN_H_
 #define UI_GFX_DPI_WIN_H_
 
 #include "ui/gfx/gfx_export.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 
 namespace gfx {
 
 // Initialization of the scale factor that should be applied for rendering
 // in this process. Must be called before attempts to call any of the getter
 // methods below in this file, e.g. in the early toolkit/resource bundle setup.
 // This can be called multiple times during various tests, but subsequent calls
 // have no effect.
 GFX_EXPORT void InitDeviceScaleFactor(float scale);
 
 GFX_EXPORT Size GetDPI();
 
 // Gets the scale factor of the display. For example, if the display DPI is
-// 96 then the scale factor is 1.0.
+// 96 then the scale factor is 1.0. Note that this is the "desktop" scale, which
+// may be differnt than GetModernUIScale().
 GFX_EXPORT float GetDPIScale();
 
+// Gets the scale factor of the modern (metro) UI display. Returns 1.0 for
+// unscaled or "not running on win8+"
+GFX_EXPORT float GetModernUIScale();
+
 // Tests to see if the command line flag "--high-dpi-support" is set.
 GFX_EXPORT bool IsHighDPIEnabled();
 
 GFX_EXPORT bool IsInHighDPIMode();
 
 GFX_EXPORT void EnableHighDPISupport();
 
 // TODO(kevers|girard):  Move above methods into win namespace.
 
 namespace win {
@@ skipping 26 matching lines @@
 
 // Win7 and Win8 send touch events scaled according to the current DPI
 // scaling. Win8.1 corrects this, and sends touch events in DPI units.
 // This function returns the appropriate scaling factor for touch events.
 GFX_EXPORT double GetUndocumentedDPITouchScale();
 
 }  // namespace win
 }  // namespace gfx
 
 #endif  // UI_GFX_DPI_WIN_H_