Add clear() to ContextHubEventLogger

Test: unit tests
Bug: 217576459
Change-Id: If9aab16975807e8fa482f4be0f389bb81c1d52cd

services/core/java/com/android/server/location/contexthub/ContextHubEventLogger.java

@@ -19,6 +19,8 @@ package com.android.server.location.contexthub;
 import android.hardware.location.NanoAppMessage;
 import android.util.Log;
 
+import java.util.Collection;
+
 /**
  * A class to log events and useful metrics within the Context Hub service.
  *
@@ -216,6 +218,18 @@ public class ContextHubEventLogger {
         return sInstance;
     }
 
+    /**
+     * Clears all queues of events.
+     */
+    public synchronized void clear() {
+        for (Collection<?> deque:
+                new Collection<?>[] {mNanoappLoadEventQueue, mNanoappUnloadEventQueue,
+                                     mMessageFromNanoappQueue, mMessageToNanoappQueue,
+                                     mContextHubRestartEventQueue}) {
+            deque.clear();
+        }
+    }
+
     /**
      * Logs a nanoapp load event
      *