Update the behaviour of the FirebasePerformanceSessionSubcriber to better match early initialization in AQS. (#7184)

This sets the subscriber in FirebasePerfEarly - allowing AQS to send a
session sooner.

The removal of
`SessionManager.getInstance().initializeGaugeCollection();` seems like
the right solution given an AQS will be created ASAP.

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: tejasd

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

@@ -21,7 +21,8 @@
 import com.google.firebase.perf.application.AppStateMonitor;
 import com.google.firebase.perf.config.ConfigResolver;
 import com.google.firebase.perf.metrics.AppStartTrace;
-import com.google.firebase.perf.session.SessionManager;
+import com.google.firebase.perf.session.FirebasePerformanceSessionSubscriber;
+import com.google.firebase.sessions.api.FirebaseSessionsDependencies;
 import java.util.concurrent.Executor;
 
 /**
@@ -41,6 +42,10 @@ public FirebasePerfEarly(
     ConfigResolver configResolver = ConfigResolver.getInstance();
     configResolver.setApplicationContext(context);
 
+    // Register FirebasePerformance as a subscriber ASAP - which will start collecting gauges if the
+    // FirebaseSession is verbose.
+    FirebaseSessionsDependencies.register(new FirebasePerformanceSessionSubscriber(configResolver));
+
     AppStateMonitor appStateMonitor = AppStateMonitor.getInstance();
     appStateMonitor.registerActivityLifecycleCallbacks(context);
     appStateMonitor.registerForAppColdStart(new FirebasePerformanceInitializer());
@@ -50,13 +55,5 @@ public FirebasePerfEarly(
       appStartTrace.registerActivityLifecycleCallbacks(context);
       uiExecutor.execute(new AppStartTrace.StartFromBackgroundRunnable(appStartTrace));
     }
-
-    // TODO: Bring back Firebase Sessions dependency to watch for updates to sessions.
-
-    // In the case of cold start, we create a session and start collecting gauges as early as
-    // possible.
-    // There is code in SessionManager that prevents us from resetting the session twice in case
-    // of app cold start.
-    SessionManager.getInstance().initializeGaugeCollection();
   }
 }

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

@@ -37,15 +37,12 @@
 import com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck;
 import com.google.firebase.perf.metrics.HttpMetric;
 import com.google.firebase.perf.metrics.Trace;
-import com.google.firebase.perf.session.FirebasePerformanceSessionSubscriber;
 import com.google.firebase.perf.session.SessionManager;
 import com.google.firebase.perf.transport.TransportManager;
 import com.google.firebase.perf.util.Constants;
 import com.google.firebase.perf.util.ImmutableBundle;
 import com.google.firebase.perf.util.Timer;
 import com.google.firebase.remoteconfig.RemoteConfigComponent;
-import com.google.firebase.sessions.api.FirebaseSessionsDependencies;
-import com.google.firebase.sessions.api.SessionSubscriber;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.net.URL;
@@ -96,8 +93,6 @@ public class FirebasePerformance implements FirebasePerformanceAttributable {
   // once during initialization and cache it.
   private final ImmutableBundle mMetadataBundle;
 
-  private final SessionSubscriber sessionSubscriber;
-
   /** Valid HttpMethods for manual network APIs */
   @StringDef({
     HttpMethod.GET,
@@ -171,7 +166,6 @@ public static FirebasePerformance getInstance() {
       this.mPerformanceCollectionForceEnabledState = false;
       this.configResolver = configResolver;
       this.mMetadataBundle = new ImmutableBundle(new Bundle());
-      this.sessionSubscriber = new FirebasePerformanceSessionSubscriber(false);
       return;
     }
     FirebaseSessionsEnforcementCheck.setEnforcement(BuildConfig.ENFORCE_LEGACY_SESSIONS);
@@ -189,8 +183,6 @@ public static FirebasePerformance getInstance() {
     sessionManager.setApplicationContext(appContext);
 
     mPerformanceCollectionForceEnabledState = configResolver.getIsPerformanceCollectionEnabled();
-    sessionSubscriber = new FirebasePerformanceSessionSubscriber(isPerformanceCollectionEnabled());
-    FirebaseSessionsDependencies.register(sessionSubscriber);
 
     if (logger.isLogcatEnabled() && isPerformanceCollectionEnabled()) {
       logger.info(
@@ -466,9 +458,4 @@ private static ImmutableBundle extractMetadata(Context appContext) {
   Boolean getPerformanceCollectionForceEnabledState() {
     return mPerformanceCollectionForceEnabledState;
   }
-
-  @VisibleForTesting
-  SessionSubscriber getSessionSubscriber() {
-    return sessionSubscriber;
-  }
 }

firebase-perf/src/main/java/com/google/firebase/perf/session/FirebasePerformanceSessionSubscriber.kt

@@ -16,17 +16,20 @@
 
 package com.google.firebase.perf.session
 
+import com.google.firebase.perf.config.ConfigResolver
 import com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck
 import com.google.firebase.sessions.api.SessionSubscriber
 
-class FirebasePerformanceSessionSubscriber(override val isDataCollectionEnabled: Boolean) :
-  SessionSubscriber {
+class FirebasePerformanceSessionSubscriber(val configResolver: ConfigResolver) : SessionSubscriber {
 
   override val sessionSubscriberName: SessionSubscriber.Name = SessionSubscriber.Name.PERFORMANCE
 
+  override val isDataCollectionEnabled: Boolean
+    get() = configResolver.isPerformanceCollectionEnabled ?: false
+
   override fun onSessionChanged(sessionDetails: SessionSubscriber.SessionDetails) {
     val currentPerfSession = SessionManager.getInstance().perfSession()
-    // TODO(b/394127311): Add logic to deal with app start gauges.
+    // TODO(b/394127311): Add logic to deal with app start gauges if necessary.
     FirebaseSessionsEnforcementCheck.checkSession(currentPerfSession, "onSessionChanged")
 
     val updatedSession = PerfSession.createWithId(sessionDetails.sessionId)

firebase-perf/src/main/java/com/google/firebase/perf/session/SessionManager.java

@@ -54,6 +54,7 @@ public final PerfSession perfSession() {
   private SessionManager() {
     // session should quickly updated by session subscriber.
     this(GaugeManager.getInstance(), PerfSession.createWithId(null));
+    FirebaseSessionsEnforcementCheck.checkSession(perfSession, "SessionManager()");
   }
 
   @VisibleForTesting