Fix a regression caused by the background fullscreen handling code.

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 14b30dae08a6784ad376598d40f2ee6d8e387da7..ed609e5714979f216af5153d852f8409e8d1d33e 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -1112,7 +1112,7 @@ void HWNDMessageHandler::TrackMouseEvents(DWORD mouse_tracking_flags) {
 
 void HWNDMessageHandler::ClientAreaSizeChanged() {
   // Ignore size changes due to fullscreen windows losing activation.
-  if (background_fullscreen_hack_)
+  if (background_fullscreen_hack_ && !sent_window_size_changing_)
     return;
   gfx::Size s = GetClientAreaBounds().size();
   delegate_->HandleClientSizeChanged(s);