Widget::ShouldUseNativeFrame is now meaningful on Linux.

ui/views/widget/widget.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/views/widget/widget.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 852 matching lines @@
   custom_frame_view->Init(this);
   return custom_frame_view;
 }
 
 bool Widget::ShouldUseNativeFrame() const {
   if (frame_type_ != FRAME_TYPE_DEFAULT)
     return frame_type_ == FRAME_TYPE_FORCE_NATIVE;
   return native_widget_->ShouldUseNativeFrame();
 }
 
+bool Widget::ShouldWindowContentsBeTransparent() const {
+  return native_widget_->ShouldWindowContentsBeTransparent();

[Matt Giuca, 2014/02/07 09:13:11]

This is the only potential behavioural change on Windows. Note that the code
path from Tab, TabStrip and Toolbar no longer goes through
Widget::ShouldUseNativeFrame, which means it doesn't honour frame_type_ (if it
is non-default). But that is never set on browser windows, to my knowledge, so I
believe this does not change the behaviour.

+}
+
 void Widget::DebugToggleFrameType() {
   if (frame_type_ == FRAME_TYPE_DEFAULT) {
     frame_type_ = ShouldUseNativeFrame() ? FRAME_TYPE_FORCE_CUSTOM :
         FRAME_TYPE_FORCE_NATIVE;
   } else {
     frame_type_ = frame_type_ == FRAME_TYPE_FORCE_CUSTOM ?
         FRAME_TYPE_FORCE_NATIVE : FRAME_TYPE_FORCE_CUSTOM;
   }
   FrameTypeChanged();
 }
@@ skipping 548 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // internal::NativeWidgetPrivate, NativeWidget implementation:
 
 internal::NativeWidgetPrivate* NativeWidgetPrivate::AsNativeWidgetPrivate() {
   return this;
 }
 
 }  // namespace internal
 }  // namespace views