[Telemetry] Add power monitoring APIs to Platform.

BUG=333504

Review URL: https://codereview.chromium.org/130253004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246206 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246206
ozone: Enumerate input devices using base::FileEnumerator

This works even if the device names are not contiguous.

Review URL: https://codereview.chromium.org/141433003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246207 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246207