Send the device scale factor from Windows 8 ASH during initialization via the MetroViewerHostMsg_Se…

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 20 matching lines @@
       reinterpret_cast<IsProcessDPIAwarePtr>(
           GetProcAddress(GetModuleHandleA("user32.dll"), "IsProcessDPIAware"));
   if (is_process_dpi_aware_func)
     return is_process_dpi_aware_func();
   return FALSE;
 }
 
 float g_device_scale_factor = 0.0f;
 
 float GetUnforcedDeviceScaleFactor() {
+  // If the global device scale factor is initialized use it. This is to ensure
+  // we use the same scale factor across all callsites. We don't use the
+  // GetDeviceScaleFactor function here because it fires a DCHECK if the
+  // g_device_scale_factor global is 0. 
+  if (g_device_scale_factor)
+    return g_device_scale_factor;
   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);
-  }
-  return result;
-}
-
 // Duplicated from Win8.1 SDK ShellScalingApi.h
 typedef enum PROCESS_DPI_AWARENESS {
     PROCESS_DPI_UNAWARE = 0,
     PROCESS_SYSTEM_DPI_AWARE = 1,
     PROCESS_PER_MONITOR_DPI_AWARE = 2
 } PROCESS_DPI_AWARENESS;
 
 typedef enum MONITOR_DPI_TYPE {
     MDT_EFFECTIVE_DPI = 0,
     MDT_ANGULAR_DPI = 1,
@@ skipping 45 matching lines @@
       reg_key.ReadValueDW(value_name, &value) == ERROR_SUCCESS) {
     return value;
   }
   return default_value;
 }
 
 }  // namespace
 
 namespace gfx {
 
-float GetModernUIScale() {
-  return GetModernUIScaleWrapper();
-}
-
 void InitDeviceScaleFactor(float scale) {
   DCHECK_NE(0.0f, scale);
   g_device_scale_factor = scale;
 }
 
 Size GetDPI() {
   static int dpi_x = 0;
   static int dpi_y = 0;
   static bool should_initialize = true;
 
@@ skipping 116 matching lines @@
 
 double GetUndocumentedDPITouchScale() {
   static double scale =
       (base::win::GetVersion() < base::win::VERSION_WIN8_1) ?
       GetUndocumentedDPIScale() : 1.0;
   return scale;
 }
 
 }  // namespace win
 }  // namespace gfx