Fix Z-order for a bubble when it appears for inactive window.

ui/views/win/hwnd_message_handler.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/win/hwnd_message_handler.h"
 
 #include <dwmapi.h>
 #include <oleacc.h>
 #include <shellapi.h>
 
@@ skipping 515 matching lines @@
     parent = ::GetWindow(hwnd(), GW_OWNER);
   gfx::CenterAndSizeWindow(parent, hwnd(), size);
 }
 
 void HWNDMessageHandler::SetRegion(HRGN region) {
   custom_window_region_.Set(region);
   ResetWindowRegion(true, true);
 }
 
 void HWNDMessageHandler::StackAbove(HWND other_hwnd) {
-  SetWindowPos(hwnd(), other_hwnd, 0, 0, 0, 0,
+  // Find a window above |other_hwnd|. If it exists, place hwnd() behind it.
+  // Otherwise, make hwnd() a top window.

[sky, 2015/06/02 16:32:57]

Why does this need to change? Also, are we sure other_hwnd is always non-null?

[vasilii, 2015/06/03 13:47:39]

The previous implementation should be called StackBelow().
We are not sure. If other_hwnd == 0 then it's a bug in the caller because it
doesn't make sense. The only caller DesktopWindowTreeHostWin::StackAbove()
checks this condition.

+  HWND next_window = GetNextWindow(other_hwnd, GW_HWNDPREV);
+  SetWindowPos(hwnd(), next_window ? next_window : HWND_TOP, 0, 0, 0, 0,
                SWP_NOSIZE | SWP_NOMOVE | SWP_NOACTIVATE);
 }
 
 void HWNDMessageHandler::StackAtTop() {
   SetWindowPos(hwnd(), HWND_TOP, 0, 0, 0, 0,
                SWP_NOSIZE | SWP_NOMOVE | SWP_NOACTIVATE);
 }
 
 void HWNDMessageHandler::Show() {
   if (IsWindow(hwnd())) {
@@ skipping 2189 matching lines @@
     SetWindowPos(hwnd(), NULL, 0, 0, 0, 0, flags | SWP_HIDEWINDOW);
     SetWindowPos(hwnd(), NULL, 0, 0, 0, 0, flags | SWP_SHOWWINDOW);
   }
   // WM_DWMCOMPOSITIONCHANGED is only sent to top level windows, however we want
   // to notify our children too, since we can have MDI child windows who need to
   // update their appearance.
   EnumChildWindows(hwnd(), &SendDwmCompositionChanged, NULL);
 }
 
 }  // namespace views