GitLab

This CL:
- Moves ConvertReturnValue to IndexedDBReturnValue
- Moves ConvertBlobInfo to IndexedDBBlobInfo
- Moves ConvertAndEraseValue to IndexedDBValue

These are needed by a later change to move code out of
IndexedDBCallbacks and use Mojo's native async return calls, instead.

Bug: 717812
Change-Id: I9f02a26eb024a3e790eddc16185d426cf530108e
Reviewed-on: https://chromium-review.googlesource.com/c/1336660
Commit-Queue: Chase Phillips <cmp@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609420}