Renames WmWindowUserData and converts to using aura

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 7926e0c1de12d9bc135a414ea3e88d757b55c712..e247379fc590926d1f53abce75e7af66e5d5bd74 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -306,11 +306,10 @@ void Shell::OnLockStateChanged(bool locked) {
 #ifndef NDEBUG
   // Make sure that there is no system modal in Lock layer when unlocked.
   if (!locked) {
-    std::vector<WmWindow*> containers = wm::GetContainersFromAllRootWindows(
-        kShellWindowId_LockSystemModalContainer,
-        WmWindow::Get(GetPrimaryRootWindow()));
-    for (WmWindow* container : containers)
-      DCHECK(container->GetChildren().empty());
+    aura::Window::Windows containers = wm::GetContainersFromAllRootWindows(
+        kShellWindowId_LockSystemModalContainer, GetPrimaryRootWindow());
+    for (aura::Window* container : containers)
+      DCHECK(container->children().empty());
   }
 #endif
 }