Make browser windows override_redirect when dragging tabs.

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
index 236fb0884bb753694f82dc9af222848015650eb5..71e74fb73bab98378f50ee479fb0cb40e02ccde7 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
@@ -304,7 +304,8 @@ void DesktopWindowTreeHostX11::OnNativeWidgetCreated(
   // TODO(erg): Unify this code once the other consumer goes away.
   SwapNonClientEventHandler(
       scoped_ptr<ui::EventHandler>(new X11WindowEventFilter(this)).Pass());
-  SetUseNativeFrame(params.type == Widget::InitParams::TYPE_WINDOW &&
+  SetUseNativeFrame((params.type == Widget::InitParams::TYPE_WINDOW ||
+                     params.type == Widget::InitParams::TYPE_DRAG_BROWSER) &&
                     !params.remove_standard_frame);
 
   x11_window_move_client_.reset(new X11DesktopWindowMoveClient);
@@ -1099,6 +1100,9 @@ void DesktopWindowTreeHostX11::InitX11Window(
       swa.override_redirect = True;
       window_type = atom_cache_.GetAtom("_NET_WM_WINDOW_TYPE_DND");
       break;
+    case Widget::InitParams::TYPE_DRAG_BROWSER:
+      swa.override_redirect = True;
+      break;
     default:
       window_type = atom_cache_.GetAtom("_NET_WM_WINDOW_TYPE_NORMAL");
       break;
@@ -1279,6 +1283,14 @@ void DesktopWindowTreeHostX11::InitX11Window(
   OnAcceleratedWidgetAvailable();
 }
 
+void DesktopWindowTreeHostX11::RemapWindow() {
+  XUnmapWindow(xdisplay_, xwindow_);
+  XSetWindowAttributes swa;
+  swa.override_redirect = False;

[Daniel Erat, 2015/12/28 21:33:02]

i wouldn't have expected a method named RemapWindow() to additionally change the
window's override-redirect attribute. maybe rename it to RemapAsNormalWindow()?

[stapelberg, 2016/01/18 17:22:23]

Done.

+  XChangeWindowAttributes(xdisplay_, xwindow_, CWOverrideRedirect, &swa);
+  XMapWindow(xdisplay_, xwindow_);
+}
+
 gfx::Size DesktopWindowTreeHostX11::AdjustSize(
     const gfx::Size& requested_size_in_pixels) {
   std::vector<gfx::Display> displays =