LevelDBWrapper: Support sending old values to leveldb wrapper when changing items

Old value parameter to Put() and Delete() calls. The parameter will be used
in next CLs to send notifications when the cache does not store values.

BUG=764127

Change-Id: I26320985265ccc66c66907770447818b94192537
Reviewed-on: https://chromium-review.googlesource.com/661417
Reviewed-by: Marijn Kruisselbrink <[email protected]>
Reviewed-by: Greg Kerr <[email protected]>
Commit-Queue: Siddhartha S <[email protected]>
Cr-Commit-Position: refs/heads/master@{#508493}
8 files changed