From 34d7742abb00aba077e865ef48ffb783578503c7 Mon Sep 17 00:00:00 2001
From: ferhatb <ferhat@gmail.com>
Date: Wed, 22 Apr 2020 14:29:44 -0700
Subject: [PATCH 1/2] Batch systemFontChange messages

---
 lib/web_ui/lib/src/engine/util.dart | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/lib/web_ui/lib/src/engine/util.dart b/lib/web_ui/lib/src/engine/util.dart
index 5063d71df9469..2979838112854 100644
--- a/lib/web_ui/lib/src/engine/util.dart
+++ b/lib/web_ui/lib/src/engine/util.dart
@@ -461,11 +461,23 @@ void applyWebkitClipFix(html.Element containerElement) {
 
 final ByteData _fontChangeMessage = JSONMessageCodec().encodeMessage(<String, dynamic>{'type': 'fontsChange'});
 
+// Font load callbacks will typically arrive in sequence, we want to prevent
+// sendFontChangeMessage of causing multiple synchronous rebuilds.
+// This flag ensures we properly schedule a single call to framework.
+bool _fontChangeScheduled = false;
+
 FutureOr<void> sendFontChangeMessage() async {
   if (window._onPlatformMessage != null)
-    window.invokeOnPlatformMessage(
-      'flutter/system',
-      _fontChangeMessage,
-      (_) {},
-    );
+    if (!_fontChangeScheduled) {
+      _fontChangeScheduled = true;
+      // Batch updates into next animationframe.
+      html.window.requestAnimationFrame((num _) {
+        _fontChangeScheduled = false;
+        window.invokeOnPlatformMessage(
+          'flutter/system',
+          _fontChangeMessage,
+              (_) {},
+        );
+      });
+    }
 }

From ce9dedd2bbbc7b61e3ad0cfcba79ff07bc1b59c2 Mon Sep 17 00:00:00 2001
From: ferhatb <ferhat@gmail.com>
Date: Thu, 23 Apr 2020 16:10:42 -0700
Subject: [PATCH 2/2] Update test for async

---
 lib/web_ui/test/text/font_loading_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/web_ui/test/text/font_loading_test.dart b/lib/web_ui/test/text/font_loading_test.dart
index 441212c47dcf8..3ec78a53aa871 100644
--- a/lib/web_ui/test/text/font_loading_test.dart
+++ b/lib/web_ui/test/text/font_loading_test.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 // @dart = 2.6
+import 'dart:async';
 import 'dart:convert';
 import 'dart:html' as html;
 import 'dart:typed_data';
@@ -85,6 +86,9 @@ Future<void> main() async {
           responseType: 'arraybuffer');
       await ui.loadFontFromList(Uint8List.view(response.response),
           fontFamily: 'Blehm');
+      final Completer<void> completer = Completer();
+      html.window.requestAnimationFrame( (_) { completer.complete(true); } );
+      await(completer.future);
       window.onPlatformMessage = oldHandler;
       expect(actualName, 'flutter/system');
       expect(message, '{"type":"fontsChange"}');