aura: Destroy the compositor before destroying the backing window.

ui/gfx/win/window_impl.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/gfx/win/window_impl.h"
 
 #include <list>
 
 #include "base/debug/alias.h"
 #include "base/memory/singleton.h"
@@ skipping 201 matching lines @@
   }
   if (!destroyed)
     destroyed_ = NULL;
 
   CheckWindowCreated(hwnd_);
 
   // The window procedure should have set the data for us.
   CHECK_EQ(this, GetWindowUserData(hwnd));
 }
 
+void WindowImpl::Destroy() {

[Ben Goodger (Google), 2014/01/14 21:48:03]

you actually can't rely on people calling this function.

for example, Windows might destroy your window, and just send you a WM_DESTROY
to let you know it did.

WM_DESTROY - "Windows is destroying your window, and the HWND is still valid. Do
some cleanup that needs the HWND to be alive. There is no way out."
WM_NCDESTROY - "Windows destroyed your window. The HWND is now bogus. Goodbye."

+  DestroyWindow(hwnd());
+  hwnd_ = NULL;

[Ben Goodger (Google), 2014/01/14 21:48:03]

... and so this should be set in a handler for WM_NCDESTROY in WndProc below.

[danakj, 2014/01/14 21:58:41]

Oh I see. The handler for WM_NCDESTROY appears to be in hwnd_message_handler.cc,
so from there I called SetDestroyed(), a method on this class that sets hwnd_ =
NULL. Then I DCHECK that the hwnd is NULL out in the
DesktopWindowTreeHostWin::HandleDestroyed.

+}
+
 HICON WindowImpl::GetDefaultWindowIcon() const {
   return NULL;
 }
 
 LRESULT WindowImpl::OnWndProc(UINT message, WPARAM w_param, LPARAM l_param) {
   LRESULT result = 0;
 
   // Handle the message if it's in our message map; otherwise, let the system
   // handle it.
   if (!ProcessWindowMessage(hwnd_, message, w_param, l_param, result))
@@ skipping 31 matching lines @@
   return window->OnWndProc(message, w_param, l_param);
 }
 
 ATOM WindowImpl::GetWindowClassAtom() {
   HICON icon = GetDefaultWindowIcon();
   ClassInfo class_info(initial_class_style(), icon);
   return ClassRegistrar::GetInstance()->RetrieveClassAtom(class_info);
 }
 
 }  // namespace gfx