mash: Convert all of //ash/system to use WmShelf

ash/test/ash_test_base.cc

Index: ash/test/ash_test_base.cc
diff --git a/ash/test/ash_test_base.cc b/ash/test/ash_test_base.cc
index 6baece0302c6e9359b12954709a180e139f0a968..c83c6c68b5a442068131bee20f12c8f4ec1ed41a 100644
--- a/ash/test/ash_test_base.cc
+++ b/ash/test/ash_test_base.cc
@@ -9,9 +9,7 @@
 
 #include "ash/common/ash_switches.h"
 #include "ash/common/wm/window_positioner.h"
-#include "ash/common/wm_root_window_controller.h"
 #include "ash/common/wm_shell.h"
-#include "ash/common/wm_window.h"
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/ime/input_method_event_handler.h"
 #include "ash/shell.h"
@@ -209,14 +207,6 @@ bool AshTestBase::SupportsHostWindowResize() {
   return AshTestHelper::SupportsHostWindowResize();
 }
 
-// static
-WmShelf* AshTestBase::GetPrimaryShelf() {
-  return WmShell::Get()
-      ->GetPrimaryRootWindow()
-      ->GetRootWindowController()
-      ->GetShelf();
-}
-
 void AshTestBase::UpdateDisplay(const std::string& display_specs) {
   DisplayManagerTestApi().UpdateDisplay(display_specs);
 }