Remove unused observer

Summary:
^

This was replaced by `ApplicationRef`

Reviewed By: antonk52

Differential Revision: D39313539

fbshipit-source-id: ad9b5c3ed963046ba0349fd5112bb9cb5de7640b

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/ApplicationObserver.kt

@@ -1,99 +0,0 @@
-/*
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-package com.facebook.flipper.plugins.uidebugger.core
-
-import android.app.Activity
-import android.app.Application
-import android.os.Bundle
-import android.view.View
-import java.lang.ref.WeakReference
-
-class ApplicationObserver(val application: Application) : Application.ActivityLifecycleCallbacks {
-  interface ActivityStackChangedListener {
-    fun onActivityStackChanged(stack: List<Activity>)
-  }
-
-  interface ActivityDestroyedListener {
-    fun onActivityDestroyed(activity: Activity)
-  }
-
-  private val rootsResolver: RootViewResolver
-  private val activities: MutableList<WeakReference<Activity>>
-  private var activityStackChangedlistener: ActivityStackChangedListener? = null
-  private var activityDestroyedListener: ActivityDestroyedListener? = null
-
-  override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {
-    activities.add(WeakReference<Activity>(activity))
-    activityStackChangedlistener?.let { listener ->
-      listener.onActivityStackChanged(this.activitiesStack)
-    }
-  }
-  override fun onActivityStarted(activity: Activity) {}
-  override fun onActivityResumed(activity: Activity) {}
-  override fun onActivityPaused(activity: Activity) {}
-  override fun onActivityStopped(activity: Activity) {}
-  override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {}
-  override fun onActivityDestroyed(activity: Activity) {
-    val activityIterator: MutableIterator<WeakReference<Activity>> = activities.iterator()
-
-    while (activityIterator.hasNext()) {
-      if (activityIterator.next().get() === activity) {
-        activityIterator.remove()
-      }
-    }
-
-    activityDestroyedListener?.let { listener -> listener.onActivityDestroyed(activity) }
-
-    activityStackChangedlistener?.let { listener ->
-      listener.onActivityStackChanged(this.activitiesStack)
-    }
-  }
-
-  fun setActivityStackChangedListener(listener: ActivityStackChangedListener?) {
-    activityStackChangedlistener = listener
-  }
-
-  fun setActivityDestroyedListener(listener: ActivityDestroyedListener?) {
-    activityDestroyedListener = listener
-  }
-
-  val activitiesStack: List<Activity>
-    get() {
-      val stack: MutableList<Activity> = ArrayList<Activity>(activities.size)
-      val activityIterator: MutableIterator<WeakReference<Activity>> = activities.iterator()
-      while (activityIterator.hasNext()) {
-        val activity: Activity? = activityIterator.next().get()
-        if (activity == null) {
-          activityIterator.remove()
-        } else {
-          stack.add(activity)
-        }
-      }
-      return stack
-    }
-
-  val rootViews: List<View>
-    get() {
-      val roots = rootsResolver.listActiveRootViews()
-      roots?.let { roots ->
-        val viewRoots: MutableList<View> = ArrayList<View>(roots.size)
-        for (root in roots) {
-          viewRoots.add(root.view)
-        }
-        return viewRoots
-      }
-
-      return emptyList()
-    }
-
-  init {
-    rootsResolver = RootViewResolver()
-    application.registerActivityLifecycleCallbacks(this)
-    activities = ArrayList<WeakReference<Activity>>()
-  }
-}