Update unit tests

Author: tejasd

firebase-perf/src/main/java/com/google/firebase/perf/session/gauges/GaugeManager.java

@@ -419,4 +419,9 @@ private long getMemoryGaugeCollectionFrequencyMs(
       return memoryGaugeCollectionFrequency;
     }
   }
+
+  @VisibleForTesting
+  void setApplicationProcessState(ApplicationProcessState applicationProcessState) {
+    this.applicationProcessState = applicationProcessState;
+  }
 }