mash: remove more shell/shelf WmWindow usage.

ash/aura/shell_port_classic.cc

Index: ash/aura/shell_port_classic.cc
diff --git a/ash/aura/shell_port_classic.cc b/ash/aura/shell_port_classic.cc
index 0e977f51549af9273b2c31bbfd90726a4497195f..0c8a8fc3930fb63c77b597c6e818d1718542818b 100644
--- a/ash/aura/shell_port_classic.cc
+++ b/ash/aura/shell_port_classic.cc
@@ -78,15 +78,13 @@ Config ShellPortClassic::GetAshConfig() const {
   return Config::CLASSIC;
 }
 
-WmWindow* ShellPortClassic::GetPrimaryRootWindow() {
-  return WmWindow::Get(
-      Shell::Get()->window_tree_host_manager()->GetPrimaryRootWindow());
+aura::Window* ShellPortClassic::GetPrimaryRootWindow() {
+  return Shell::Get()->window_tree_host_manager()->GetPrimaryRootWindow();
 }
 
-WmWindow* ShellPortClassic::GetRootWindowForDisplayId(int64_t display_id) {
-  return WmWindow::Get(
-      Shell::Get()->window_tree_host_manager()->GetRootWindowForDisplayId(
-          display_id));
+aura::Window* ShellPortClassic::GetRootWindowForDisplayId(int64_t display_id) {
+  return Shell::Get()->window_tree_host_manager()->GetRootWindowForDisplayId(
+      display_id);
 }
 
 const display::ManagedDisplayInfo& ShellPortClassic::GetDisplayInfo(