refactor: restore deprecated constructor in TracedUnaryCallable

Author: blakeli0

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedUnaryCallable.java

@@ -51,11 +51,23 @@ public class TracedUnaryCallable<RequestT, ResponseT> extends UnaryCallable<Requ
   private final UnaryCallable<RequestT, ResponseT> innerCallable;
   private final ApiTracerFactory tracerFactory;
   private final SpanName spanName;
-  private final ApiTracerContext apiTracerContext;
+  @Nullable private final ApiTracerContext apiTracerContext;
   @Nullable private final ResourceNameExtractor<RequestT> resourceNameExtractor;
 
 
 
+  @Deprecated
+  public TracedUnaryCallable(
+      UnaryCallable<RequestT, ResponseT> innerCallable,
+      ApiTracerFactory tracerFactory,
+      SpanName spanName) {
+    this.innerCallable = innerCallable;
+    this.tracerFactory = tracerFactory;
+    this.spanName = spanName;
+    this.apiTracerContext = null;
+    this.resourceNameExtractor = null;
+  }
+
   public TracedUnaryCallable(
       UnaryCallable<RequestT, ResponseT> innerCallable,
       ApiTracerFactory tracerFactory,
@@ -77,10 +89,15 @@ public TracedUnaryCallable(
    */
   @Override
   public ApiFuture<ResponseT> futureCall(RequestT request, ApiCallContext context) {
-    ApiTracer tracer =
-        tracerFactory.newTracer(
-            context.getTracer(),
-            apiTracerContext.withResourceNameExtractor(request, resourceNameExtractor));
+    ApiTracer tracer;
+    if (apiTracerContext != null) {
+      tracer =
+          tracerFactory.newTracer(
+              context.getTracer(),
+              apiTracerContext.withResourceNameExtractor(request, resourceNameExtractor));
+    } else {
+      tracer = tracerFactory.newTracer(context.getTracer(), spanName, OperationType.Unary);
+    }
     TraceFinisher<ResponseT> finisher = new TraceFinisher<>(tracer);
 
     try {