message: Add forward declarations of friend'ed classes.
diff: @@ -29,6 +29,9 @@ limitations under the License.
  namespace tensorflow {
  namespace jit {
  +class DeviceInfoCache;
  +class DeviceSet;
  +
  // Instances of DeviceId represent TensorFlow devices as integers.
  //
  // This helps avoid having to manipulate device names as strings when
  