[IndexedDB] Fixed blobs being saved on disk during incognito mode

R=cmp@chromium.org

Bug: 941965
Change-Id: I37fec1b2c90c7e3bd2b6c20115e307b2f4efebf5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1524097
Auto-Submit: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Chase Phillips <cmp@chromium.org>
Reviewed-by: Chase Phillips <cmp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#640961}
6 files changed