Add always-on-top property to app windows

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 f7b624ee8ab5c1deace5dc03862f34f47d124d86..cdd3af36cbb110e85772d26ead063a6b30f6f847 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -686,6 +686,10 @@ bool HWNDMessageHandler::IsMaximized() const {
   return !!::IsZoomed(hwnd());
 }
 
+bool HWNDMessageHandler::IsAlwaysOnTop() const {
+  return (GetWindowLong(hwnd(), GWL_EXSTYLE) & WS_EX_TOPMOST) != 0;
+}
+
 bool HWNDMessageHandler::RunMoveLoop(const gfx::Vector2d& drag_offset,
                                      bool hide_on_escape) {
   ReleaseCapture();