Disk cache v3: The main index table.

The IndexTable controls what entries are stored in the cache.
This class provides a memory-only view of the underlying structures
that store "the index"

BUG=241277
TEST=net_unittests

Review URL: https://codereview.chromium.org/53313004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244027 0039d316-1c4b-4281-b951-d872f2087c98
Refactor device description out of PrivetDeviceLister

This should enable the creation of a separate PrivetDeviceResolver class, which
should be useful.

BUG=332182

Review URL: https://codereview.chromium.org/107293012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244028 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244028