Use a single ToplevelWindowEventHandler for the ash::Shell

ui/views/widget/native_widget_aura.cc

Index: ui/views/widget/native_widget_aura.cc
diff --git a/ui/views/widget/native_widget_aura.cc b/ui/views/widget/native_widget_aura.cc
index c5c93072aaf03ba52bfb03eba9b309960bcdf9cd..0797b18655c366f482fbe68c36d8c66ac0a252e0 100644
--- a/ui/views/widget/native_widget_aura.cc
+++ b/ui/views/widget/native_widget_aura.cc
@@ -648,18 +648,21 @@ Widget::MoveLoopResult NativeWidgetAura::RunMoveLoop(
     Widget::MoveLoopEscapeBehavior escape_behavior) {
   // |escape_behavior| is only needed on windows when running the native message
   // loop.
-  if (window_ && window_->parent() &&
-      aura::client::GetWindowMoveClient(window_->parent())) {
-    SetCapture();
-    aura::client::WindowMoveSource window_move_source =
-        source == Widget::MOVE_LOOP_SOURCE_MOUSE ?
-        aura::client::WINDOW_MOVE_SOURCE_MOUSE :
-        aura::client::WINDOW_MOVE_SOURCE_TOUCH;
-    if (aura::client::GetWindowMoveClient(window_->parent())->RunMoveLoop(
-            window_, drag_offset, window_move_source) ==
-        aura::client::MOVE_SUCCESSFUL) {
-      return Widget::MOVE_LOOP_SUCCESSFUL;
-    }
+  if (!window_ || !window_->GetRootWindow())
+    return Widget::MOVE_LOOP_CANCELED;
+  aura::client::WindowMoveClient* move_client =
+      aura::client::GetWindowMoveClient(window_->GetRootWindow());
+  if (!move_client)
+    return Widget::MOVE_LOOP_CANCELED;
+
+  SetCapture();
+  aura::client::WindowMoveSource window_move_source =
+      source == Widget::MOVE_LOOP_SOURCE_MOUSE ?
+      aura::client::WINDOW_MOVE_SOURCE_MOUSE :
+      aura::client::WINDOW_MOVE_SOURCE_TOUCH;
+  if (move_client->RunMoveLoop(window_, drag_offset, window_move_source) ==
+          aura::client::MOVE_SUCCESSFUL) {
+    return Widget::MOVE_LOOP_SUCCESSFUL;
   }
   return Widget::MOVE_LOOP_CANCELED;
 }