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In rare cases it was possible a renderer vanished taking the
PaintPreviewDocumentData with it before the PaintPreviewClient was
destroyed. This resulted in the invocation of an empty callback
causing a crash. This CL audits all use of document_data to ensure it is
safe.

Bug: 1062434
Change-Id: Ie5e800755902f66d5c6b3a46f956fb522bde97f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2106383Reviewed-by: Mehran Mahmoudi <mahmoudi@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#751349}