Addressing rayo's comments

Author: ankitaj224

firebase-installations/src/main/java/com/google/firebase/installations/Utils.java

@@ -41,13 +41,15 @@ private Utils(Clock clock) {
 
   // Factory method that always returns the same Utils instance.
   public static Utils getInstance() {
-    if (singleton == null) {
-      singleton = new Utils(SystemClock.getInstance());
-    }
-    return singleton;
+    return getInstance(SystemClock.getInstance());
   }
 
-  public static Utils getTestInstance(Clock clock) {
+  /**
+   * Returns an Utils instance. {@link Utils#getInstance()} defines the clock used. NOTE: If a Utils
+   * instance has already been initialized, the parameter will be ignored and the existing instance
+   * will be returned.
+   */
+  public static Utils getInstance(Clock clock) {
     if (singleton == null) {
       singleton = new Utils(clock);
     }

firebase-installations/src/main/java/com/google/firebase/installations/remote/FirebaseInstallationServiceClient.java

@@ -33,7 +33,6 @@
 import com.google.firebase.inject.Provider;
 import com.google.firebase.installations.FirebaseInstallationsException;
 import com.google.firebase.installations.FirebaseInstallationsException.Status;
-import com.google.firebase.installations.Utils;
 import com.google.firebase.installations.remote.InstallationResponse.ResponseCode;
 import com.google.firebase.platforminfo.UserAgentPublisher;
 import java.io.BufferedReader;
@@ -115,7 +114,7 @@ public FirebaseInstallationServiceClient(
     this.context = context;
     this.userAgentPublisher = publisher;
     this.heartbeatInfo = heartbeatInfo;
-    this.requestLimiter = new RequestLimiter(Utils.getInstance());
+    this.requestLimiter = new RequestLimiter();
   }
 
   /**

firebase-installations/src/main/java/com/google/firebase/installations/remote/RequestLimiter.java

@@ -42,6 +42,11 @@ class RequestLimiter {
     this.utils = utils;
   }
 
+  RequestLimiter() {
+    // Util class is injected to ease mocking & testing the system time.
+    this.utils = Utils.getInstance();
+  }
+
   // Based on the response code, calculates the next request time to communicate with the FIS
   // servers.
   public synchronized void setNextRequestTime(int responseCode) {

firebase-installations/src/test/java/com/google/firebase/installations/FirebaseInstallationsTest.java

@@ -152,7 +152,7 @@ public void setUp() {
     persistedInstallation.clearForTesting();
 
     fakeClock = new FakeClock(5000000L);
-    utils = Utils.getTestInstance(fakeClock);
+    utils = Utils.getInstance(fakeClock);
     firebaseInstallations =
         new FirebaseInstallations(
             executor,