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The drag-and-drop origin surface may get suddenly destroyed, when it is
a xdg-popup, eg. dragging bookmarks bar's menu item in Chrome, which
currently leads to crashes in WaylandDataDragController. This CL fixes
it as well as adds unit tests to prevent future similar regressions.

R=msisov@igalia.com, tonikitoo@igalia.com

Bug: 1143707
Test: Covered by ozone_unittests --ozone-platform=wayland
Change-Id: I1bac3032c428d3456bf644b35f869ec6ff5122e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2635449
Auto-Submit: Nick Yamane <nickdiego@igalia.com>
Commit-Queue: Maksim Sisov <msisov@igalia.com>
Reviewed-by: Maksim Sisov <msisov@igalia.com>
Cr-Commit-Position: refs/heads/master@{#845701}