Revert changes for grpc_metadata_batch

src/core/lib/channel/call_tracer.h

@@ -41,17 +41,17 @@ class CallTracer {
     // Please refer to `grpc_transport_stream_op_batch_payload` for details on
     // arguments.
     virtual void RecordSendInitialMetadata(
-        const grpc_metadata_batch& send_initial_metadata, uint32_t flags) = 0;
+        grpc_metadata_batch* send_initial_metadata, uint32_t flags) = 0;
     virtual void RecordOnDoneSendInitialMetadata(gpr_atm* peer_string) = 0;
     virtual void RecordSendTrailingMetadata(
-        const grpc_metadata_batch& send_trailing_metadata) = 0;
+        grpc_metadata_batch* send_trailing_metadata) = 0;
     virtual void RecordSendMessage(const ByteStream& send_message) = 0;
     virtual void RecordReceivedInitialMetadata(
-        const grpc_metadata_batch& recv_initial_metadata, uint32_t* flags,
+        grpc_metadata_batch* recv_initial_metadata, uint32_t* flags,
         gpr_atm* peer_string) = 0;
     virtual void RecordReceivedMessage(const ByteStream& recv_message) = 0;
     virtual void RecordReceivedTrailingMetadata(
-        const grpc_metadata_batch& recv_trailing_metadata) = 0;
+        grpc_metadata_batch* recv_trailing_metadata) = 0;
     virtual void RecordCancel(grpc_error_handle cancel_error) = 0;
     // Records annotations if supported by the attached tracer library, no-op
     // otherwise.

src/cpp/ext/filters/census/open_census_call_tracer.h

@@ -33,20 +33,20 @@ class OpenCensusCallTracer : public grpc_core::CallTracer {
    public:
     ~OpenCensusCallAttemptTracer() override {}
     void RecordSendInitialMetadata(
-        const grpc_metadata_batch& /* send_initial_metadata */,
+        grpc_metadata_batch* /* send_initial_metadata */,
         uint32_t /* flags */) override {}
     void RecordOnDoneSendInitialMetadata(gpr_atm* /* peer_string */) override {}
     void RecordSendTrailingMetadata(
-        const grpc_metadata_batch& /* send_trailing_metadata */) override {}
+        grpc_metadata_batch* /* send_trailing_metadata */) override {}
     void RecordSendMessage(
         const grpc_core::ByteStream& /* send_message */) override {}
     void RecordReceivedInitialMetadata(
-        const grpc_metadata_batch& /* recv_initial_metadata */,
-        uint32_t* /* flags */, gpr_atm* /* peer_string */) override {}
+        grpc_metadata_batch* /* recv_initial_metadata */, uint32_t* /* flags */,
+        gpr_atm* /* peer_string */) override {}
     void RecordReceivedMessage(
         const grpc_core::ByteStream& /* recv_message */) override {}
     void RecordReceivedTrailingMetadata(
-        const grpc_metadata_batch& /* recv_trailing_metadata */) override {}
+        grpc_metadata_batch* /* recv_trailing_metadata */) override {}
     void RecordCancel(grpc_error_handle /* cancel_error */) override {}
     void RecordAnnotation(absl::string_view /* annotation */) override {}
     void RecordEnd(const grpc_call_final_info& /* final_info */) override {}