Refactor to support default Bluetooth pairing delegate

In order to support a default pairing delegate we need to move the agent
service provider delegate implementation from BluetoothDevice to
BluetoothAdapter while retaining the existing API.

BUG=338492
TEST=device_unittests, unit_tests, browser_tests

Review URL: https://codereview.chromium.org/148293003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252216 0039d316-1c4b-4281-b951-d872f2087c98
bool BluetoothAdapterChromeOS::IsDiscovering() const {
  if (!IsPresent())
    return false;

  BluetoothAdapterClient::Properties* properties =
      DBusThreadManager::Get()->GetBluetoothAdapterClient()->
          GetProperties(object_path_);

  return properties->discovering.value();
}

bool BluetoothAdapterChromeOS::IsDiscovering() const {
  if (!IsPresent())
    return false;

  BluetoothAdapterClient::Properties* properties =
      DBusThreadManager::Get()->GetBluetoothAdapterClient()->
          GetProperties(object_path_);

  return properties->discovering.value();
}
