Add @Singelton annotation to FirebasePerformance class and component. (#2467)

Author: visumickey

firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerformance.java

@@ -49,6 +49,7 @@
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import javax.inject.Inject;
+import javax.inject.Singleton;
 
 /**
  * The Firebase Performance Monitoring API.
@@ -60,6 +61,7 @@
  * #setPerformanceCollectionEnabled(boolean)
  * FirebasePerformance.setPerformanceCollectionEnabled(false)}.
  */
+@Singleton
 public class FirebasePerformance implements FirebasePerformanceAttributable {
 
   private static final AndroidLogger logger = AndroidLogger.getInstance();

firebase-perf/src/main/java/com/google/firebase/perf/injection/components/FirebasePerformanceComponent.java

@@ -18,13 +18,15 @@
 import com.google.firebase.perf.FirebasePerformance;
 import com.google.firebase.perf.injection.modules.FirebasePerformanceModule;
 import dagger.Component;
+import javax.inject.Singleton;
 
 /**
  * Dagger component to create FirebasePerformanceComponent Objects.
  *
  * @hide
  */
 @Component(modules = {FirebasePerformanceModule.class})
+@Singleton
 public interface FirebasePerformanceComponent {
   @NonNull
   FirebasePerformance getFirebasePerformance();