Make browser windows override_redirect when dragging tabs.

ui/aura/window_tree_host_x11.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/aura/window_tree_host_x11.h"
 
 #include <strings.h>
 #include <X11/cursorfont.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/extensions/Xrandr.h>
@@ skipping 533 matching lines @@
   // ChromeOS because ChromeOS manages all of the X windows. When running
   // ChromeOS on the desktop for the sake of debugging:
   // - Implicit pointer grab as a result of pressing a mouse button
   // - Releasing capture as a result of losing activation (FocusOut)
   // is sufficient.
 }
 
 void WindowTreeHostX11::ReleaseCapture() {
 }
 
+void WindowTreeHostX11::RemapAsNormalWindow() {

[Daniel Erat, 2016/01/19 20:36:22]

NOTREACHED() here too?

[stapelberg, 2016/01/20 13:31:09]

Done.

+}
+
 void WindowTreeHostX11::SetCursorNative(gfx::NativeCursor cursor) {
   if (cursor == current_cursor_)
     return;
   current_cursor_ = cursor;
   SetCursorInternal(cursor);
 }
 
 void WindowTreeHostX11::MoveCursorToNative(const gfx::Point& location) {
   XWarpPointer(xdisplay_, None, x_root_window_, 0, 0, 0, 0,
                bounds_.x() + location.x(),
@@ skipping 104 matching lines @@
 }
 
 namespace test {
 
 void SetUseOverrideRedirectWindowByDefault(bool override_redirect) {
   default_override_redirect = override_redirect;
 }
 
 }  // namespace test
 }  // namespace aura