[chromeos] Move files from chromeos/power to chrome/browser/chromeos/power

This is being done so that content::BrowserThread can be used in
PowerDataCollector, which is required for future changes.

BUG=312956,335816
TBR=arv

Review URL: https://codereview.chromium.org/153153002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248852 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248852