Replace window.confirm() with UI.ConfirmDialog
Replace window.confirm() with UI.ConfirmDialog

Before: https://i.imgur.com/ikLsY00.png
After: https://i.imgur.com/re8vltz.png

Fixed: 1055762
Change-Id: I16508507e9bae7e834481a651d9aff1ec92cd138
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/3242144
Reviewed-by: Simon Zünd <38944668e9e2ca98ccd0275b53370f90fa55c113@chromium.org>
Commit-Queue: Wolfgang Beyer <573aa99bb19da47d816981118f95c945310dd3f4@chromium.org>

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