Widget::ShouldUseNativeFrame is now meaningful on Linux.

ui/views/widget/widget.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_VIEWS_WIDGET_WIDGET_H_
 #define UI_VIEWS_WIDGET_WIDGET_H_
 
 #include <set>
 #include <stack>
 #include <vector>
@@ skipping 573 matching lines @@
 
   // Creates an appropriate NonClientFrameView for this widget. The
   // WidgetDelegate is given the first opportunity to create one, followed by
   // the NativeWidget implementation. If both return NULL, a default one is
   // created.
   virtual NonClientFrameView* CreateNonClientFrameView();
 
   // Whether we should be using a native frame.
   bool ShouldUseNativeFrame() const;
 
+  // Determines whether the window contents should be rendered transparently
+  // (for example, so that they can overhang onto the window title bar).
+  bool ShouldWindowContentsBeTransparent() const;

[sky, 2014/02/10 15:04:08]

This name isn't the greatest at the widget level, but I can't think of anything
that is really that much better.

+
   // Forces the frame into the alternate frame type (custom or native) depending
   // on its current state.
   void DebugToggleFrameType();
 
   // Tell the window that something caused the frame type to change.
   void FrameTypeChanged();
 
   NonClientView* non_client_view() {
     return const_cast<NonClientView*>(
         const_cast<const Widget*>(this)->non_client_view());
@@ skipping 278 matching lines @@
   // True when window movement via mouse interaction with the frame should be
   // disabled.
   bool movement_disabled_;
 
   DISALLOW_COPY_AND_ASSIGN(Widget);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_WIDGET_H_