message: Use int32 GPU kernel for StopGradient
diff: @@ -129,6 +129,12 @@ REGISTER_GPU_KERNEL(Variant);
  .HostMemory("output") \
  .TypeConstraint<type>("T"), \
  IdentityOp); \
  + REGISTER_KERNEL_BUILDER(Name("StopGradient") \
  + .Device(DEVICE_GPU) \
  + .HostMemory("input") \
  + .HostMemory("output") \
  + .TypeConstraint<type>("T"), \
  + IdentityOp); \
  REGISTER_KERNEL_BUILDER(Name("PlaceholderWithDefault") \
  .Device(DEVICE_GPU) \
  .HostMemory("input") \
  