Use CopyOnWriteArrayList in MemoryPressureRouter (#43486)

Summary:
Pull Request resolved: #43486

We use `CopyOnWriteArrayList` in other places across the React Native codebase, as it assumes that reading happens more frequently than updating. This saves us from needing to synchronize and copy when we access the list of listeners.

Changelog: [Internal]

Reviewed By: sammy-SC

Differential Revision: D54806272

fbshipit-source-id: d1b54d532edb2af3391a7e4fdc758f705621227d

Author: javache

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/MemoryPressureRouter.java

@@ -11,14 +11,12 @@
 import android.content.Context;
 import android.content.res.Configuration;
 import com.facebook.react.bridge.MemoryPressureListener;
-import java.util.Collections;
-import java.util.LinkedHashSet;
-import java.util.Set;
+import java.util.concurrent.CopyOnWriteArrayList;
 
-/** Translates and routes memory pressure events to the current catalyst instance. */
+/** Translates and routes memory pressure events. */
 public class MemoryPressureRouter implements ComponentCallbacks2 {
-  private final Set<MemoryPressureListener> mListeners =
-      Collections.synchronizedSet(new LinkedHashSet<>());
+  private final CopyOnWriteArrayList<MemoryPressureListener> mListeners =
+      new CopyOnWriteArrayList();
 
   public MemoryPressureRouter(Context context) {
     context.getApplicationContext().registerComponentCallbacks(this);
@@ -30,7 +28,9 @@ public void destroy(Context context) {
 
   /** Add a listener to be notified of memory pressure events. */
   public void addMemoryPressureListener(MemoryPressureListener listener) {
-    mListeners.add(listener);
+    if (!mListeners.contains(listener)) {
+      mListeners.add(listener);
+    }
   }
 
   /** Remove a listener previously added with {@link #addMemoryPressureListener}. */
@@ -50,11 +50,7 @@ public void onConfigurationChanged(Configuration newConfig) {}
   public void onLowMemory() {}
 
   private void dispatchMemoryPressure(int level) {
-    // copy listeners array to avoid ConcurrentModificationException if any of the listeners remove
-    // themselves in handleMemoryPressure()
-    MemoryPressureListener[] listeners =
-        mListeners.toArray(new MemoryPressureListener[mListeners.size()]);
-    for (MemoryPressureListener listener : listeners) {
+    for (MemoryPressureListener listener : mListeners) {
       listener.handleMemoryPressure(level);
     }
   }