chromeos: Rename ash::WmShelf to Shelf

ash/system/toast/toast_overlay.cc

Index: ash/system/toast/toast_overlay.cc
diff --git a/ash/system/toast/toast_overlay.cc b/ash/system/toast/toast_overlay.cc
index 1c2815b53e69a9d6885e14faced6400c04914b9a..a653304d3b767555958c6a012df4fe9a1bce6879 100644
--- a/ash/system/toast/toast_overlay.cc
+++ b/ash/system/toast/toast_overlay.cc
@@ -7,7 +7,7 @@
 #include "ash/public/cpp/ash_typography.h"
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/root_window_controller.h"
-#include "ash/shelf/wm_shelf.h"
+#include "ash/shelf/shelf.h"
 #include "ash/shell.h"
 #include "ash/strings/grit/ash_strings.h"
 #include "base/strings/string_util.h"
@@ -49,7 +49,7 @@ const int kToastMinimumWidth = 288;
 // Returns the work area bounds for the root window where new windows are added
 // (including new toasts).
 gfx::Rect GetUserWorkAreaBounds() {
-  return WmShelf::ForWindow(Shell::GetRootWindowForNewWindows())
+  return Shelf::ForWindow(Shell::GetRootWindowForNewWindows())
       ->GetUserWorkAreaBounds();
 }