Remove "upgrading to 2x DSF for lower UI scale when 2x resoruces are available" option

ash/display/display_info.cc

Index: ash/display/display_info.cc
diff --git a/ash/display/display_info.cc b/ash/display/display_info.cc
index 6a117b01c9631be2ccfbf2371072e6d8e60810a6..61432f60c14b8b54e7a8c980c4d07dab3bbafbd0 100644
--- a/ash/display/display_info.cc
+++ b/ash/display/display_info.cc
@@ -23,9 +23,6 @@
 namespace ash {
 namespace {
 
-// TODO(oshima): This feature is obsolete. Remove this after m38.
-bool allow_upgrade_to_high_dpi = false;
-
 bool use_125_dsf_for_ui_scaling = false;
 
 // Check the content of |spec| and fill |bounds| and |device_scale_factor|.
@@ -46,7 +43,7 @@ bool GetDisplayBounds(
   return false;
 }
 
-}
+}  // namespace
 
 DisplayMode::DisplayMode()
     : refresh_rate(0.0f),
@@ -86,9 +83,6 @@ DisplayInfo DisplayInfo::CreateFromSpec(const std::string& spec) {
 }
 
 // static
-void DisplayInfo::SetAllowUpgradeToHighDPI(bool enable) {
-  allow_upgrade_to_high_dpi = enable;
-}
 
 // static
 void DisplayInfo::SetUse125DSFForUIScaling(bool enable) {
@@ -292,26 +286,16 @@ void DisplayInfo::SetBounds(const gfx::Rect& new_bounds_in_native) {
 float DisplayInfo::GetEffectiveDeviceScaleFactor() const {
   if (use_125_dsf_for_ui_scaling && device_scale_factor_ == 1.25f)
     return (configured_ui_scale_ == 0.8f) ? 1.25f : 1.0f;
-
-  if (allow_upgrade_to_high_dpi && configured_ui_scale_ < 1.0f &&
-      device_scale_factor_ == 1.0f) {
-    return 2.0f;
-  } else if (device_scale_factor_ == configured_ui_scale_) {
+  if (device_scale_factor_ == configured_ui_scale_)
     return 1.0f;
-  }
   return device_scale_factor_;
 }
 
 float DisplayInfo::GetEffectiveUIScale() const {
   if (use_125_dsf_for_ui_scaling && device_scale_factor_ == 1.25f)
     return (configured_ui_scale_ == 0.8f) ? 1.0f : configured_ui_scale_;
-
-  if (allow_upgrade_to_high_dpi && configured_ui_scale_ < 1.0f &&
-      device_scale_factor_ == 1.0f) {
-    return configured_ui_scale_ * 2.0f;
-  } else if (device_scale_factor_ == configured_ui_scale_) {
+  if (device_scale_factor_ == configured_ui_scale_)
     return 1.0f;
-  }
   return configured_ui_scale_;
 }