Give Ash material design tray items the correct size and layout

ash/system/chromeos/session/logout_button_tray.cc

Index: ash/system/chromeos/session/logout_button_tray.cc
diff --git a/ash/system/chromeos/session/logout_button_tray.cc b/ash/system/chromeos/session/logout_button_tray.cc
index 1ee41f03e32e51e11da62587fd978d439667bdbd..a8f893a38d70b613b34b384dbe3aa957780238d2 100644
--- a/ash/system/chromeos/session/logout_button_tray.cc
+++ b/ash/system/chromeos/session/logout_button_tray.cc
@@ -89,7 +89,7 @@ LogoutButton::LogoutButton(views::ButtonListener* listener)
   SetBorder(std::move(border));
   set_animate_on_state_change(false);
 
-  SetMinSize(gfx::Size(0, kShelfItemHeight));
+  SetMinSize(gfx::Size(0, GetTrayConstant(TRAY_ITEM_HEIGHT_LEGACY)));
 }
 
 LogoutButton::~LogoutButton() {}