3rd part of porting Chrome Ash to Windows 7

ui/gfx/win/dpi.cc

 // 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.
 
 #include "ui/gfx/win/dpi.h"
 
 #include <windows.h>
 #include "base/command_line.h"
 #include "base/win/scoped_hdc.h"
 #include "base/win/windows_version.h"
@@ skipping 26 matching lines @@
 
 float g_device_scale_factor = 0.0f;
 
 float GetUnforcedDeviceScaleFactor() {
   return static_cast<float>(gfx::GetDPI().width()) /
       static_cast<float>(kDefaultDPIX);
 }
 
 float GetModernUIScaleWrapper() {
   float result = 1.0f;
+  // TODO(cpu) : Fix scale for Win7.
+  if (base::win::GetVersion() < base::win::VERSION_WIN8)
+    return result;
+
   typedef float(WINAPI *GetModernUIScalePtr)(VOID);
   HMODULE lib = LoadLibraryA("metro_driver.dll");
   if (lib) {
     GetModernUIScalePtr func =
         reinterpret_cast<GetModernUIScalePtr>(
         GetProcAddress(lib, "GetModernUIScale"));
     if (func)
       result = func();
     FreeLibrary(lib);
   }
@@ skipping 202 matching lines @@
 
 double GetUndocumentedDPITouchScale() {
   static double scale =
       (base::win::GetVersion() < base::win::VERSION_WIN8_1) ?
       GetUndocumentedDPIScale() : 1.0;
   return scale;
 }
 
 }  // namespace win
 }  // namespace gfx