Simplify layout of tray items and fix spacing for MD.

ash/common/system/tray/fixed_sized_image_view.cc

Index: ash/common/system/tray/fixed_sized_image_view.cc
diff --git a/ash/common/system/tray/fixed_sized_image_view.cc b/ash/common/system/tray/fixed_sized_image_view.cc
index a593b6f2a3234429de461072620dba19a293fbce..5284be071a196e9fd108b86a80871c2dd8011688 100644
--- a/ash/common/system/tray/fixed_sized_image_view.cc
+++ b/ash/common/system/tray/fixed_sized_image_view.cc
@@ -7,10 +7,7 @@
 namespace ash {
 
 FixedSizedImageView::FixedSizedImageView(int width, int height)
-    : width_(width), height_(height) {
-  SetHorizontalAlignment(views::ImageView::CENTER);
-  SetVerticalAlignment(views::ImageView::CENTER);
-}
+    : width_(width), height_(height) {}
 
 FixedSizedImageView::~FixedSizedImageView() {}