runtime: fix memory leak on release objects

When a java object is finally freed in Java, we notify the JS side to free the JS counterpart. At this time, the Java object is held weakly in Java too using a WeakReference. While the Java object is weakly held, the WeakReference is strongly kept in a HashMap never getting removed. In this PR we release the WeakReferences too on GC event ensuring that all memory is reclaimed.

Author: ammarahm-ed

test-app/runtime/src/main/java/com/tns/Runtime.java

@@ -764,6 +764,9 @@ public void notifyGc() {
     }
 
     public void notifyGc(int[] objectIds) {
+        for (int id: objectIds) {
+                weakInstances.remove(id);
+        }
         notifyGc(runtimeId, objectIds);
     }