[Files app] Add logging for every start up

Add logging as warn so it shows up in the logs file.

Add logging for:
- Earliest startup of Files app.
- Before trying to change to the initial directory.
- After finished changing to the initial directory.
- If there is no initial directory.

Change background page logs from debug to warn to have information
about the volumes initialization. We can turn this back to debug once
we figure out this bug.

These cover the bare minimal of the Files app initialization.

Add a util function to return a debug string from a give entry, to use
in the logging during startup.

Bug: 904658
Change-Id: Iaa14b8fe5ac171f4fa2cd070edadaf370e50c5f9
Reviewed-on: https://chromium-review.googlesource.com/c/1480302
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634574}
5 files changed