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

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index 13cc62cbfbbe0db0a62cf78f37d39da3f0e2ce33..ab641de27a186f83b81c5c1de0758e494b37938a 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -533,7 +533,10 @@ void HWNDMessageHandler::SetRegion(HRGN region) {
 }
 
 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);
 }