Consolidate some more ash tray constants.

ash/common/system/chromeos/audio/volume_view.cc

Index: ash/common/system/chromeos/audio/volume_view.cc
diff --git a/ash/common/system/chromeos/audio/volume_view.cc b/ash/common/system/chromeos/audio/volume_view.cc
index 571b5bf9f51b62b507c917f2a958ee974358423b..dcfb60cad0d8fbca39a2f5045ebe969943950991 100644
--- a/ash/common/system/chromeos/audio/volume_view.cc
+++ b/ash/common/system/chromeos/audio/volume_view.cc
@@ -185,8 +185,8 @@ VolumeView::VolumeView(SystemTrayItem* owner,
   more_button_->SetFocusBehavior(FocusBehavior::NEVER);
 
   device_type_ = TrayPopupUtils::CreateMoreImageView();
-  more_button_->SetBorder(views::CreateEmptyBorder(gfx::Insets(
-      0, GetTrayConstant(TRAY_POPUP_ITEM_MORE_REGION_HORIZONTAL_INSET))));
+  more_button_->SetBorder(
+      views::CreateEmptyBorder(gfx::Insets(0, kTrayPopupButtonEndMargin)));

[tdanderson, 2017/02/28 17:08:18]

nit: consider renaming to kTrayPopupButtonHorizontalMargin /  or similar and
update the documentation in tray_constants.h

[Evan Stade, 2017/03/01 04:28:54]

I removed the docs, but horizontal margin is just as problematic as end margin
since in other places it's only applied to the end (right).

   more_button_->AddChildView(device_type_);
 
   views::ImageView* more_arrow = TrayPopupUtils::CreateMoreImageView();