Add window position offset.

services/ui/ws/platform_display_default.h

Index: services/ui/ws/platform_display_default.h
diff --git a/services/ui/ws/platform_display_default.h b/services/ui/ws/platform_display_default.h
index f0f5326ce7c6ddce6c6d8b6e4c4f61fb76907191..e1fc569275f69ec790a687a58330b7400ef46cc4 100644
--- a/services/ui/ws/platform_display_default.h
+++ b/services/ui/ws/platform_display_default.h
@@ -81,6 +81,9 @@ class PlatformDisplayDefault : public PlatformDisplay,
   PlatformDisplayDelegate* delegate_ = nullptr;
   std::unique_ptr<FrameGenerator> frame_generator_;
 
+  // Fix X11 event positions when the window gets resized.
+  int window_height_offset_ = 0;
+
   display::ViewportMetrics metrics_;
   std::unique_ptr<ui::PlatformWindow> platform_window_;
   gfx::AcceleratedWidget widget_;