Add more timeline ranges for profiling hot reload (#7792)

packages/flutter/lib/src/rendering/binding.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:developer';
 import 'dart:ui' as ui show window;
 
 import 'package:flutter/foundation.dart';
@@ -227,7 +228,12 @@ abstract class RendererBinding extends BindingBase implements SchedulerBinding,
   @override
   void reassembleApplication() {
     super.reassembleApplication();
-    renderView.reassemble();
+    Timeline.startSync('Dirty Render Tree');
+    try {
+      renderView.reassemble();
+    } finally {
+      Timeline.finishSync();
+    }
     handleBeginFrame(null);
   }
 

packages/flutter/lib/src/widgets/framework.dart

@@ -1873,9 +1873,14 @@ class BuildOwner {
   ///
   /// This is expensive and should not be called except during development.
   void reassemble(Element root) {
-    assert(root._parent == null);
-    assert(root.owner == this);
-    root._reassemble();
+    Timeline.startSync('Dirty Element Tree');
+    try {
+      assert(root._parent == null);
+      assert(root.owner == this);
+      root._reassemble();
+    } finally {
+      Timeline.finishSync();
+    }
   }
 }