Host DeviceInfo: allow to write to file directly.

This allows implementations to write JSON string to file directly
instead of using HostInfoStore. This is useful for cases where
the output of a shell command is in formatted JSON, for example.

Test: run and examine output
Bug: 126233777
Change-Id: I62aea2d8904e65936ddb1d77a919b45e230d625c
1 file changed
tree: cfd65f82fb10f518903a56fea694f344680cbb98
  1. build/
  2. common/
  3. tools/
  4. OWNERS
  5. PREUPLOAD.cfg
  6. test_defs.sh