GitLab

This commit adds an interface class AccelerometerProviderInterface for
AccelerometerFileReader, to allow another mojo implementation in the
future. It also moves AccelerometerFileReader into separate source
files.

BUG=b:168434557
TEST=builds and run on kohaku

Change-Id: I6ee6e2253764a69cfe1693f792b64fa275b34a8b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2409672
Commit-Queue: Cheng-Hao Yang <chenghaoyang@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815247}