[ozone/wayland] Omit buffer commit and OnSubmission when window is null

In tab dragging, when dragged window snaps to a tab strip, the
corresponding WaylandWindow is destroyed. The corresponding buffer queue
in gpu process is expected to be destroyed soon, so omit upcoming
overlay commits should be safe.

Change-Id: I38923f461e9c1eb3ac63d72237989194b2f887d5
Bug: 1114767
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2353554Reviewed-by: Nick Yamane <nickdiego@igalia.com>
Reviewed-by: Maksim Sisov (GMT+3) <msisov@igalia.com>
Commit-Queue: Kramer Ge <fangzhoug@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797739}

ui/ozone/platform/wayland/host/wayland_buffer_manager_host.cc

@@ -807,9 +807,18 @@ void WaylandBufferManagerHost::CommitOverlays(
   TRACE_EVENT0("wayland", "WaylandBufferManagerHost::CommitOverlays");
 
   DCHECK(error_message_.empty());
+
+  if (widget == gfx::kNullAcceleratedWidget) {
+    error_message_ = "Invalid widget.";
+    TerminateGpuProcess();
+  }
   WaylandWindow* window =
       connection_->wayland_window_manager()->GetWindow(widget);
-  DCHECK(window);
+  // In tab dragging, window may have been destroyed when buffers reach here. We
+  // omit buffer commits and OnSubmission, because the corresponding buffer
+  // queue in gpu process should be destroyed soon.
+  if (!window)
+    return;
 
   window->CommitOverlays(overlays);
 }