chore(spanner): review comments

Author: harshachinta

google-cloud-spanner/src/main/java/com/google/cloud/spanner/TransactionRunnerImpl.java

@@ -642,13 +642,14 @@ public void onTransactionMetadata(Transaction transaction, boolean shouldInclude
      */
     @Override
     public void onPrecommitToken(MultiplexedSessionPrecommitToken token) {
-      if (token == null) return;
+      if (token == null) {
+        return;
+      }
       synchronized (precommitTokenLock) {
         if (this.latestPrecommitToken == null
             || token.getSeqNum() > this.latestPrecommitToken.getSeqNum()) {
           this.latestPrecommitToken = token;
-          System.out.println("Updating precommit token to " + this.latestPrecommitToken);
-          txnLogger.log(Level.ALL, "Updating precommit token to " + this.latestPrecommitToken);
+          txnLogger.log(Level.FINE, "Updating precommit token to " + this.latestPrecommitToken);
         }
       }
     }
@@ -981,7 +982,6 @@ public long[] batchUpdate(Iterable<Statement> statements, UpdateOption... update
             }
           }
 
-          // TODO(sriharshach): check if we need to get precommit_token from response.getResultSets
           if (response.hasPrecommitToken()) {
             onPrecommitToken(response.getPrecommitToken());
           }

google-cloud-spanner/src/test/java/com/google/cloud/spanner/MockSpannerServiceImpl.java

@@ -1093,10 +1093,12 @@ private void returnResultSet(
       Transaction transaction = getTemporaryTransactionOrNull(transactionSelector);
       metadata = metadata.toBuilder().setTransaction(transaction).build();
     }
-    resultSet = resultSet.toBuilder().setMetadata(metadata).build();
+    ResultSet.Builder resultSetBuilder = resultSet.toBuilder();
+    resultSetBuilder.setMetadata(metadata);
     if (session.getMultiplexed()) {
-      resultSet = resultSet.toBuilder().setPrecommitToken(getResultSetPrecommitToken()).build();
+      resultSetBuilder.setPrecommitToken(getResultSetPrecommitToken());
     }
+    resultSet = resultSetBuilder.build();
     responseObserver.onNext(resultSet);
   }