Corrections based on comments regarding dead lock and nitpick

Capture strong self during async observer registration

Author: JesusRojass

FirebasePerformance/Sources/AppActivity/FPRTraceBackgroundActivityTracker.m

@@ -37,13 +37,10 @@ - (instancetype)init {
     } else {
       _traceBackgroundState = FPRTraceStateForegroundOnly;
     }
-    if ([NSThread isMainThread]) {
-      [self registerNotificationObservers];
-    } else {
-      dispatch_sync(dispatch_get_main_queue(), ^{
-        [self registerNotificationObservers];
-      });
-    }
+    __strong typeof(self) strongSelf = self;
+    dispatch_async(dispatch_get_main_queue(), ^{
+      [strongSelf registerNotificationObservers];
+    });
   }
   return self;
 }

FirebasePerformance/Tests/Unit/FPRTraceBackgroundActivityTrackerTest.m

@@ -81,7 +81,7 @@ - (void)testObservers_synchronousRegistrationAddsObserver {
                     object:[UIApplication sharedApplication]]);
 }
 
-/** Tests rapid creation and deallocation to verify race condition fix. */
+/** Tests rapid creation and deallocation to verify race condition. */
 - (void)testRapidCreationAndDeallocation_noRaceCondition {
   for (int i = 0; i < 100; i++) {
     @autoreleasepool {