ash: Highlight the items in the uber-tray popup when hovering.

ash/system/user/tray_user.cc

Index: ash/system/user/tray_user.cc
diff --git a/ash/system/user/tray_user.cc b/ash/system/user/tray_user.cc
index c355635582f580c01bdb6f4d69643a07d0a6cac6..6c86014d28fa4be2cb5e0ddc02bb8522eb7fd40f 100644
--- a/ash/system/user/tray_user.cc
+++ b/ash/system/user/tray_user.cc
@@ -104,6 +104,7 @@ class UserView : public views::View,
     CHECK(status != ash::user::LOGGED_IN_NONE);
     SetLayoutManager(new views::BoxLayout(views::BoxLayout::kVertical,
           0, 0, 0));
+    set_background(views::Background::CreateSolidBackground(SK_ColorWHITE));
 
     if (status != ash::user::LOGGED_IN_GUEST)
       AddUserInfo();