This change introduces more detailed reporting of why downloads are paused in
the download manager.
First, it adds new, more detailed status constants in android.provider.Downloads
for when a download is paused, in place of the old catch-all
STATUS_RUNNING_PAUSED. I've eliminated some dead code there as well to ease the
change.
Second, in the public API, it changes COLUMN_ERROR_CODE to COLUMN_REASON, which
now reports useful info for STATUS_PAUSED in addition to STATUS_FAILED. It adds
some new PAUSED_* constants for reason values when a download is paused, and
adds code to generate these values appropriately.
Change-Id: Ie617d1c2c59357375e19466086923ace5e2fb122
3e8c1d3a46