Properly release PrintDialogGtk2 when its parent window is destroyed.
Properly release PrintDialogGtk2 when its parent window is destroyed.

Review URL: https://codereview.chromium.org/1715153002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#376653}

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