Introduce user customization of external HighDPI mode for 4K monitor.

ash/display/display_info.cc

 // Copyright (c) 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.
 
 #include <stdio.h>
 #include <string>
 #include <vector>
 
 #include "ash/display/display_info.h"
 #include "base/logging.h"
@@ skipping 11 matching lines @@
 
 namespace ash {
 namespace {
 
 // TODO(oshima): This feature is obsolete. Remove this after m38.
 bool allow_upgrade_to_high_dpi = false;
 
 }
 
 DisplayMode::DisplayMode()
-    : refresh_rate(0.0f), interlaced(false), native(false) {}
+    : refresh_rate(0.0f),
+      interlaced(false),
+      native(false),
+      ui_scale(1.0f),
+      device_scale_factor(1.0f) {}
 
 DisplayMode::DisplayMode(const gfx::Size& size,
                          float refresh_rate,
                          bool interlaced,
                          bool native)
     : size(size),
       refresh_rate(refresh_rate),
       interlaced(interlaced),
-      native(native) {}
+      native(native),
+      ui_scale(1.0f),
+      device_scale_factor(1.0f) {}
+
+gfx::Size DisplayMode::GetSizeInDIP() const {
+  gfx::SizeF size_dip(size);
+  size_dip.Scale(ui_scale);
+  size_dip.Scale(1.0f / device_scale_factor);
+  return gfx::ToFlooredSize(size_dip);
+}
 
 // satic
 DisplayInfo DisplayInfo::CreateFromSpec(const std::string& spec) {
   return CreateFromSpecWithID(spec, gfx::Display::kInvalidDisplayID);
 }
 
 // static
 void DisplayInfo::SetAllowUpgradeToHighDPI(bool enable) {
   allow_upgrade_to_high_dpi = enable;
 }
@@ skipping 288 matching lines @@
 }
 
 bool DisplayInfo::IsColorProfileAvailable(
     ui::ColorCalibrationProfile profile) const {
   return std::find(available_color_profiles_.begin(),
                    available_color_profiles_.end(),
                    profile) != available_color_profiles_.end();
 }
 
 }  // namespace ash