Update shelf spacing in Chrome OS according to the MD specs

ash/root_window_controller_unittest.cc

Index: ash/root_window_controller_unittest.cc
diff --git a/ash/root_window_controller_unittest.cc b/ash/root_window_controller_unittest.cc
index 6f974ddd1c063253f1a5bd995ee71de708a921fb..6cb3617691478f75d981082822a5478b4fcda12a 100644
--- a/ash/root_window_controller_unittest.cc
+++ b/ash/root_window_controller_unittest.cc
@@ -199,8 +199,8 @@ TEST_F(RootWindowControllerTest, MoveWindows_Basic) {
   EXPECT_EQ("100,20 100x100",
             normal->GetNativeView()->GetBoundsInRootWindow().ToString());
 
-  // Maximized area on primary display has 47px (ash::kShelfSize) inset at the
-  // bottom.
+  // Maximized area on primary display has 47px for non-md and 48px for md
+  // (defined in ash::SHELF_SIZE) inset at the bottom.
 
   // First clear fullscreen status, since both fullscreen and maximized windows
   // share the same desktop workspace, which cancels the shelf status.