defaultPassthroughServiceImplementation: default

Specify default argument to dPSI which allows the following calls:
- dPSI("foo", 1 /* maxThreads */);
- dPSI("foo");
- dPSI(1 /* maxThreads */);
- dPSI();

Test: compiles
Change-Id: If1f7100527583dd7d01c17c107282b043d710ee3
diff --git a/transport/include/hidl/LegacySupport.h b/transport/include/hidl/LegacySupport.h
index 9ee0635..3cc23f3 100644
--- a/transport/include/hidl/LegacySupport.h
+++ b/transport/include/hidl/LegacySupport.h
@@ -71,7 +71,7 @@
  * Return value is exit status.
  */
 template<class Interface>
-int defaultPassthroughServiceImplementation(std::string name = "default",
+int defaultPassthroughServiceImplementation(std::string name,
                                             size_t maxThreads = 1) {
     configureRpcThreadpool(maxThreads, true);
     status_t result = registerPassthroughServiceImplementation<Interface>(name);
@@ -83,6 +83,10 @@
     joinRpcThreadpool();
     return 0;
 }
+template<class Interface>
+int defaultPassthroughServiceImplementation(size_t maxThreads = 1) {
+    return defaultPassthroughServiceImplementation<Interface>("default", maxThreads);
+}
 
 }  // namespace hardware
 }  // namespace android