linux_aura: Default to system titlebars under some window managers.

ui/base/x/x11_util.h

 // 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.
 
 #ifndef UI_BASE_X_X11_UTIL_H_
 #define UI_BASE_X_X11_UTIL_H_
 
 // This file declares utility functions for X11 (Linux only).
 //
 // These functions do not require the Xlib headers to be included (which is why
@@ skipping 206 matching lines @@
 UI_BASE_EXPORT void SetWindowRole(XDisplay* display,
                                   XID window,
                                   const std::string& role);
 
 // Get |window|'s parent window, or None if |window| is the root window.
 UI_BASE_EXPORT XID GetParentWindow(XID window);
 
 // Walk up |window|'s hierarchy until we find a direct child of |root|.
 XID GetHighestAncestorWindow(XID window, XID root);
 
+// Determine whether we should default to native decorations or the custom
+// frame based on the currently-running window manager.
+UI_BASE_EXPORT bool GetCustomFramePrefDefault();
+
 static const int kAllDesktops = -1;
 // Queries the desktop |window| is on, kAllDesktops if sticky. Returns false if
 // property not found.
 bool GetWindowDesktop(XID window, int* desktop);
 
 // Translates an X11 error code into a printable string.
 UI_BASE_EXPORT std::string GetX11ErrorString(XDisplay* display, int err);
 
 // Implementers of this interface receive a notification for every X window of
 // the main display.
@@ skipping 153 matching lines @@
  private:
   ::Cursor cursor_;
   XDisplay* display_;
 
   DISALLOW_COPY_AND_ASSIGN(XScopedCursor);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_X_X11_UTIL_H_