Linux Aura: Use managed tab dragging when possible (Reland)

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
index a4b68b382218dec15d642952423d1fa23f8bb604..88d33ce6387e3b3d10396abc676095fbabc14e78 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
@@ -26,6 +26,12 @@
 #include "ui/views/views_export.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host.h"
 
+namespace aura {
+namespace client {
+class WindowMoveClient;
+}
+}
+
 namespace gfx {
 class ImageSkia;
 class ImageSkiaRep;
@@ -39,7 +45,6 @@ class XScopedEventSelector;
 namespace views {
 class DesktopDragDropClientAuraX11;
 class DesktopWindowTreeHostObserverX11;
-class X11DesktopWindowMoveClient;
 class X11WindowEventFilter;
 
 class VIEWS_EXPORT DesktopWindowTreeHostX11
@@ -282,6 +287,9 @@ class VIEWS_EXPORT DesktopWindowTreeHostX11
   XDisplay* xdisplay_;
   ::Window xwindow_;
 
+  // |xwindow_| is managed iff it is not override-redirect.
+  bool is_managed_;
+
   // Events selected on |xwindow_|.
   std::unique_ptr<ui::XScopedEventSelector> xwindow_events_;
 
@@ -343,7 +351,7 @@ class VIEWS_EXPORT DesktopWindowTreeHostX11
   DesktopDragDropClientAuraX11* drag_drop_client_;
 
   std::unique_ptr<ui::EventHandler> x11_non_client_event_filter_;
-  std::unique_ptr<X11DesktopWindowMoveClient> x11_window_move_client_;
+  std::unique_ptr<aura::client::WindowMoveClient> x11_window_move_client_;
 
   // TODO(beng): Consider providing an interface to DesktopNativeWidgetAura
   //             instead of providing this route back to Widget.