For #21309: add profiler markers on global layout.

app/src/main/java/org/mozilla/fenix/HomeActivity.kt

@@ -207,6 +207,7 @@ open class HomeActivity : LocaleAwareAppCompatActivity(), NavHostActivity {
 
         binding = ActivityHomeBinding.inflate(layoutInflater)
         setContentView(binding.root)
+        ProfilerMarkers.addListenerForOnGlobalLayout(components.core.engine, this, binding.root)
 
         // Must be after we set the content view
         if (isVisuallyComplete) {

app/src/main/java/org/mozilla/fenix/perf/ProfilerMarkers.kt

@@ -4,9 +4,12 @@
 
 package org.mozilla.fenix.perf
 
+import android.app.Activity
 import android.view.View
+import android.view.ViewTreeObserver
 import androidx.core.view.doOnPreDraw
 import mozilla.components.concept.base.profiler.Profiler
+import mozilla.components.concept.engine.Engine
 
 /**
  * A container for functions for when adding a profiler marker is less readable
@@ -14,9 +17,27 @@ import mozilla.components.concept.base.profiler.Profiler
  */
 object ProfilerMarkers {
 
+    fun addListenerForOnGlobalLayout(engine: Engine, activity: Activity, rootView: View) {
+        // We define the listener in a non-anonymous class to avoid memory leaks with the activity.
+        val listener = MarkerGlobalLayoutListener(engine, activity::class.simpleName ?: "null")
+        rootView.viewTreeObserver.addOnGlobalLayoutListener(listener)
+    }
+
     fun homeActivityOnStart(rootContainer: View, profiler: Profiler?) {
         rootContainer.doOnPreDraw {
             profiler?.addMarker("onPreDraw", "expected first frame via HomeActivity.onStart")
         }
     }
 }
+
+/**
+ * A global layout listener that adds a profiler marker on global layout.
+ */
+class MarkerGlobalLayoutListener(
+    private val engine: Engine,
+    private val activityName: String,
+) : ViewTreeObserver.OnGlobalLayoutListener {
+    override fun onGlobalLayout() {
+        engine.profiler?.addMarker("onGlobalLayout", activityName)
+    }
+}