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* Install the Context's persistent data directory in /data.
* Use the existence of /data as the canonical signal for enabling
  incognito mode. (Tests will still use the --incognito switch
  override.)
  ** Add a smoke test suite for running in incognito mode.
* Configure disk_cache to use SimpleCacheBackend. The default persistent
  cache backend will break because it relies on mmap(), which isn't
  supported by minfs.
* Add semantic validation for the |data_directory| handle.
  ** Add tests to exercise validation.
* Remove GetPackageRoot(), since there's no reason to not use
  PathService(DIR_SOURCE_ROOT, ...) anymore.
* Remove unused Fuchsia-specific path DIR_FUCHSIA_RESOURCES.

Bug: 840598
Change-Id: I3efdb072cc4ee8f7df21992d6a84a1b548bb7fed
Reviewed-on: https://chromium-review.googlesource.com/1232524Reviewed-by: Scott Graham <scottmg@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592513}