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This API was only able to delete local-only data and because ios/web_view
will no longer save local-only data, this API is now obsolete.

Change-Id: I9e919d84ac9651d72a82eb656bb9678d3d60e05b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2148459Reviewed-by: Hiroshi Ichikawa <ichikawa@chromium.org>
Commit-Queue: John Wu <jzw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#759095}