message: Fixing grpc namespace to fix some OSS build compatibility issue.
diff: @@ -314,7 +314,7 @@ class GrpcTpuStream {
  class GrpcTpuDriver : public TpuDriver {
  public:
  explicit GrpcTpuDriver(const TpuDriverConfig& config,
  - std::shared_ptr<::grpc_impl::ChannelCredentials> creds,
  + std::shared_ptr<::grpc::ChannelCredentials> creds,
  int32_t client_id)
  : config_(config), creds_(creds), client_id_(client_id) {
  SystemInfo system_info;
  @@ -336,7 +336,9 @@ class GrpcTpuDriver : public TpuDriver {
  return;
  }
  auto status = Close();
  - LOG_IF(ERROR, !status.ok()) << status;
  + if (!status.ok()) {
  + LOG(ERROR) << status;
  + }
  }
  void QuerySystemInfo(SystemInfo* system_info) override;
  @@ -419,7 +421,7 @@ class GrpcTpuDriver : public TpuDriver {
  static std::unique_ptr<grpc::CloudTpuDriver::Stub> CreateTpuDriverStub(
  const TpuDriverConfig& config,
  - std::shared_ptr<::grpc_impl::ChannelCredentials> creds);
  + std::shared_ptr<::grpc::ChannelCredentials> creds);
  uint32_t client_id() const { return client_id_; }
  @@ -428,7 +430,7 @@ class GrpcTpuDriver : public TpuDriver {
  std::unique_ptr<GrpcTpuStream> AllocateStream(int32_t core_id);
  const TpuDriverConfig config_;
  - std::shared_ptr<::grpc_impl::ChannelCredentials> creds_;
  + std::shared_ptr<::grpc::ChannelCredentials> creds_;
  const uint32_t client_id_;
  // Map from stream IDs to streams.
  absl::flat_hash_map<int32_t, std::unique_ptr<GrpcTpuStream>> streams_;
  @@ -942,7 +944,7 @@ std::shared_ptr<Event> GrpcTpuStream::ExecuteProgram(
  /*static*/ std::unique_ptr<grpc::CloudTpuDriver::Stub>
  GrpcTpuDriver::CreateTpuDriverStub(
  const TpuDriverConfig& config,
  - std::shared_ptr<grpc_impl::ChannelCredentials> creds) {
  + std::shared_ptr<::grpc::ChannelCredentials> creds) {
  ::grpc::ChannelArguments args;
  args.SetMaxReceiveMessageSize(std::numeric_limits<int>::max());
  args.SetMaxSendMessageSize(std::numeric_limits<int>::max());
  @@ -1052,7 +1054,7 @@ Status GrpcTpuDriver::Close() {
  xla::StatusOr<std::unique_ptr<TpuDriver>> CreateGrpcTpuDriver(
  const TpuDriverConfig& config,
  - std::shared_ptr<::grpc_impl::ChannelCredentials> creds) {
  + std::shared_ptr<::grpc::ChannelCredentials> creds) {
  auto stub = GrpcTpuDriver::CreateTpuDriverStub(config, creds);
  ::grpc::ClientContext ctx;
  ctx.set_fail_fast(false);
  